Blood group systems

• Blood group antigens are encoded by alleles at single gene locus.
• Altogether 30 blood group systems have been identified.
• These antigens are integral part of RBC membrane or are carried on GPI linked proteins.
• When transfusing, ABO mismatch may be fatal, where as mismatch of other blood groups is initially is harmless.
• They are detected in the laboratory by using antigen antibody reactions
• Antigen antibody reaction and hence agglutination of RBCs can be enhanced by following methods:
  • Overcoming the negative charge (Zeta potential) on the surface of RBCs. This is done by using IgM antibodies against IgG, which bridge the gap between 2 IgG molecules. Zeta potential can also be decreased by using bovine albumin and enzymes such as papain.
  • Appropriate antigen antibody ratio (Usually 2 volumes of serum and one volume of 2-4% cell suspension is used)
  • Maintaining pH between 6.6 and 7.5.
  • Incubation of reaction mixture for about 1 hour
  • Using low ionic strength saline (LISS)
  • Centrifugation
• DNA based typing of blood group antigens is possible now, as genes of most of blood group antigens have been identified and cloned. Advantages of this technique include
  • Typing of patients who are recently transfused is possible
  • Typing can be done even if RBCs are coated with immunoglobulins.
  • Typing is possible when commercial antisera are not available.
  • Identifying weak D and partial D.
  • Resolving blood group typing discrepancies
  • Typing of fetus to determine the risk of HDN.

ABO blood group system

• Individuals, who lack the antigens of ABO system, have the corresponding antibody in their serum. These are naturally occurring antibodies of IgM type.
• These antibodies are capable of causing intravascular hemolysis (through complement mediated cytotoxicity), if transfused with incompatible blood.
• These antigens are present on all cells of the body.

• Locus for ABO genes is located on chromosome 9.
• It follows Mendelian law of inheritance, where A and B genes are dominant, while O gene is recessive.
• ABO genes do not synthesize antigens directly. The products of A, B, and H genes are transferase enzymes.
• Product of H gene converts basic precursor substance to H substance.
• O gene is an amorph (no gene product), hence O group RBCs contain only H substance.
• H substance is subsequently converted to A or B antigens by products of A or B gene respectively.
• Bombay blood group people do not contain H gene, instead they contain h gene. This h gene is amorph with no gene product. Hence these people have only basic precursor substance and not H substance. Hence once should not transfuse O blood group RBCs to them.
• A group RBC which reacts to anti A1 lectin is called A1 blood group, while the one which does not react is called A2 blood group. 80% of A are A1 type. Type A2 individuals express substantially less A antigen. Some Type A2 and A2B individuals have anti-A1 antibodies, that bind to A1 type RBCs at non-physiological/ room temperature. If they are reactive at 37 degree C, then such patients must be transfused with A2 or O group RBCs.
• ABO antigens are expressed on endothelial cells as well. Hence ABO compatibility is typically required for solid organ transplantation.
• Routine ABO testing procedures
  • Forward typing: Patient’s RBCs are mixed with anti A and anti B antisera.
  • Reverse grouping: Patient’s serum is tested against RBCs of known blood group.
• Procedures for blood grouping
  • Slide/ tile method
  • Tube method
  • Microplate method
  • Gel card method

Rh Blood group System

• Important to know because
  • Hemolytic disease of newborn may occur in Rh negative pregnant women with Rh positive fetus.
  • It can induce allo reactive antibodies which pose problem during subsequent blood transfusions.
• Genes of Rh system are located on chromosome 1
• There are 3 pairs of genes: Cc, Dd and Ee, but only 5 antigens- C, c, D, E, e.
• Rh gene travels in set of 3. Ex: CDe, CDE etc
• Out of all, presence or absence of D gene is most important. When D antigen is present RBCs react to anti-D and such cells are called Rh D positive.
• C, c, E and e are less immunogenic. Such antigens are expressed as D-U. For testing D-U, along with anti D,IgM antibodies raised against antiD are used. These IgM antibodies bridge the gap between 2 anti D molecules which are bound to RBCs.
• Significance of D-U.
  • In donors it is considered as D positive.
  • In recipients it is considered D negative, i.e. D-U positive patients must be given Rh negative blood.

Other blood group systems

• Individuals may develop antibodies, if they are transfused with blood containing antigens, which are absent on their own red blood cells.
• It is important to subject every patient’s samples to an antibody screen prior to transfusion to detect any unexpected antibodies. If antibody screen is positive then it is necessary to identify the antibody and transfuse blood, lacking the corresponding antigen.
• Other blood group systems are
  • MNS
  • P
  • Lutheran
  • Kell
  • Lewis
  • Duffy
  • Kidd
  • Diego
  • Yt
  • Xg
  • Scianna
  • Dombrock
  • Colton
  • LW
  • Chido
  • H
  • Kx
  • Gerbich
  • Cromer
  • Knops
  • Indian
  • Ok
  • Raph
  • JMH
  • I
  • GLOB
  • Gil

Blood group antibodies:

• 2 types
  • Allo antibodies: They react with antigens present on RBCs of other people.
  • Auto antibodies: They react with antigens present on patient's own RBCs.
• Depending on mode of sensitization
  • Naturally occurring: No apparent sensitization
  • Immune: Occur following sensitization (pregnancy/ transfusion) 

Compatibility testing

• Set of tests done to ensure survival of transfused RBCs in the recipient.
• Done to know whether patient has unexpected RBC antibodies.

Alternate compatibility choices

• In case of emergency Rh positive RBC can be given to male patient and women who have completed their family, provided no preformed anti D is demonstrable in their sera.
• Compatibility testing includes following steps
  • Review of patient's past blood bank history and records
  • ABO and Rh typing of donor and recipient.
  • Antibody screening of patient and donor.
  • Cross match: 
    • Major cross match: Patient's serum is mixed with donor RBCs, and confirmed that there are no unexpected antibodies.
    • Minor cross match: Patient's RBCs are mixed with donor's plasma.

Collection of blood:

Donor selection:

• For whole blood transfusion, donor should not donate twice in 3 months period.
• Age: 18-60 years
• Weight: More than 50Kgs
• Normal blood pressure, pulse and temperature.
• Hemoglobin :>12.5gm/dL
• No history of anemia, jaundice, kidney disease, heart disease, epilepsy, HIV, hepatitis, tuberculosis, cancer etc.
• Should not be pregnant or lactating
• There should not be history of tattoo, IV drug abuse, acupuncture, body piercing, immunization.
• Should not have consumed medicines such as aspirin

Blood collection and processing

• Approximately 450ml blood is collected over 7-10min in a bag containing 70ml of CPDA anticoagulant.
• It is kept at room temperature till processing.
• Functions of various chemicals present in blood collection bag
  • Citrate: Chelates calcium and stops coagulation
  • Dextrose: Necessary for metabolism of red cells
  • Citric acid: Prevents caramelization of dextrose during autoclaving.
  • Adenine: Enhances ATP production.
• Separation into components helps in economy/ optimal use of blood which is a limited community resource and also minimizes hazards of whole blood transfusion.
• Whole blood is seldom used now.
• Component preparation is done using sedimentation and centrifugation principles.
• When light spin is applied whole blood gets separated into platelet rich plasma and packed red cells. Platelet rich plasma is furtherseparated intoplatelet concentrate and FFP by subjecting to heavy spin. 
• FFP is slowly thawed to 4 degree C and at that temperature supernatant is removed to get cryoprecipitate.

Apheresis

• It is a procedure in which whole blood is withdrawn from the donor and after retaining the desired component, remaining portion of blood is infused back into the donor.
• 2 types of apheresis machines
  • Intermittent flow centrifugation Ex: Haemonetics
  • Continuous flow centrifugation- Ex: Cobe spectra
• For platelet donation, donor’s platelet count must be more than 1,00,000/cmm
• Interval between 2 apheresis procedures must be at least 48hrs.
• Time needed for platelet pheresis is 90min.
• Adverse effect to donor- Citrate toxicity (Numbness around the mouth due to hypocalcemia)
• If plasma is being collected, in one sitting not more than 500ml plasma can be collected.
• Indications for therapeutic plasmapheresis
  • Removal of antibodies: Hemolytic disease of newborn, Guillain-Barre syndrome, acute polyneuritis, Good Pasture syndrome, acquired hemophilia
  • Removal of immune complexes: Rapidly progressive glomerulonephritis, SLE, polyarteritisnodosa, cryoglobulinemia
  • Hyperviscosity syndrome: Waldenstorm’smacroglobulinemia, multiple myeloma
  • Removal of toxins- Hepatic failure, renal failure
  • Replacement of deficient plasma component: Thrombotic thrombocytopenic purpura, hemolytic uremic syndrome
• Indications for therapeutic cytapheresis
  • Erythrocytapheresis: Acute complications of sickle cell disease, Praphylaxis against frequent stroke/ pain crisis in sickle cell disease, severe malarial infection, hemochromatosis
  • Leukapheresis: Leukemia with hyperleukocytosis syndrome, cutaneous T cell lymphoma
  • Platelet pheresis: Symptomatic thrombocytosis
• Advantages of apheresis
  • Exposure to fewer and repeatedly tested donors, hence less chances of infections.
  • Higher leukoreduction and less RBC contamination
  • Permits immediate release of product from blood bank
  • Better platelet count improvement
  • Products can be collected from special attribute donors (HLA or HPA matched donors and IgA deficient)

Complications associated with transfusion of blood products

• Transfusion transmitted diseases: Hepatitis B, Hepatitis C, HIV, CMV, HTLV, Syphilis, Malaria, toxoplasma, microfilaria etc
• Acute hemolytic transfusion reaction: 
  • Occurs within 24 hours of transfusion
  • Occurs due to mismatched blood transfusion (Usually ABO, but can also occur with Duffy and Kell, as individuals produce antibodies against antigens that are absent on their RBC surfaces). 
  • Presents with burning pain at infusion site, flushing, fever, chills, flank pain/ backache, red/ brown colored urine, chest tightness, hypotension, DIC, and acute renal failure
  • Severity depends on potency of anti A and anti B antibodies. 
  • 2 mechanisms of hemolysis:
    • Intravascular hemolysis: Antibody causing complement activation binds an RBC antigen
    • Extravascular hemolysis: Antibody targeting an RBC antigen opsonizes the RBC, which leads to sequestration and phagocytosis by macrophages of the reticuloendothelial system (liver, spleen, bone marrow)
  • If such reaction is seen, 
    • STOP transfusion, inform blood bank
    • Send following things to blood bank: Untransfused remaining blood, EDTA and plain blood samples, urine sample 
    • Send hemogram, RFT, LFT, LDH, DCT, ICT, PT/APTT, blood culture
    • Aggressive IV hydration to remove free hemoglobin in blood (avoid volume overload)
    • Corticosteroids, antihistamines, and epinephrine in the case of airway compromise
    • Exchange transfusion as last resort
    • Supportive treatment including hemodialysis and treatment of DIC
  • Peripheral smear shows: keratocytes, helmet cells, bite cells, blister cells, spherocytes, or microspherocytes
• Delayed hemolytic transfusion reaction:
  • Occurs usually 2 weeks after transfusion but can occur up to 30 days post-transfusion
  • Results from an amnestic response, a secondary immune reaction of the immune system to a foreign RBC antigen previously encountered (pregnancy/ previous transfusions)
  • Commonly seen with sickle cell anemia patients
  • Hemolysis is usually complement mediated. This results in hyperhemolysis, i.e. destruction of patient’s own RBCs.
  • Often they have reticulocytopenia (reasons for this is not clear)
  • Symptoms are less pronounced compared to an acute hemolytic reaction (unexplained fall in hemoglobin and mild jaundice about one week after blood transfusion sometimes along with dark urine)
  • Mortality is rare
  • Implicated antigens: Rh, Kidd, Duffy, Kell, and the MNS constituents
  • If this problem is suspected: 
    • Inform blood bank
    • Send CBC, reticulocyte count, LFT, RFT, LDH, Monospecific DCT, urine analysis
    • Antibody testing and compared with the patient's pretransfusion sample to evaluate for new autoantibodies
  • Treatment
    • Supportive care
    • Optimize erythropoiesis: Intravenous iron and erythropoietin
    • Immunomodulatory therapies: complement inhibition (eculizumab- 600 to 900mg weekly, up to 4 doses), steroids (1 to 4mg/kg/d of prednisone), intravenous immunoglobulin (0.4 to 1g/kg/d for 3-5 days, up to total dose of 2g/kg), and/or B cell depletion (Rituximab- 375mg/m2, dosed again in 1-2 weeks)
    • Minimize future transfusions: Most important, as even fully crossmatch compatible, antigen negative RBC units may exacerbate the ongoing hemolysis
  • Prevention: Transfuse RBCs prophylactically antigen matched for at least C/c, E/e, and K (and possibly for Fya /Fyb, Jka/Jkb, and S/s as well)
• Febrile non-hemolytic reaction- Fever with chills. Occurs due to presence of antibodies to WBCs. Self-limiting.
• Allergic reaction- Urticaria to anaphylaxis
• Transfusion associated circulatory overload (TACO)
  • Occurs due to excessive volume or high speed of transfusion with severely anemic patient with compromised heart functioning.
  • Presents with breathlessness, cough and raised JVP.
  • NT-Pro BNP is raised
  • Prevention: Diuretics prior to transfusion, slow transfusion in elderly people
• Transfusion related lung injury (TRALI)
  • Common with FFP transfusion
  • Sequestration of neutrophils occurs in lung tissue due to underlying clinical condition. Upon transfusion of blood products containing human leucocyte antibodies, there is activation of sequestered neutrophils, leading to tissue damage and edema.
  • Present with respiratory distress, hypoxia, fever with no signs of left heart failure
  • Treatment: High dose methyl prednisolone with respiratory support
• Post transfusion purpura- Refer “other acquired thrombocytopenias” chapter in “platelet disorders” section
• Transfusion related graft Vs Host disease
  • Seen especially when blood from close relatives (HLA haplo-identical) is being transfused.
  • It is seen in even if blood from unrelated donor is given to patients with conditions causing reduced cellular immunity. Such conditions include stem cell transplantation, congenital immunodeficiency and Hodgkin’s lymphoma.
  • It is caused by the donor’s lymphocytes engrafting the recipient and reacting against host antigen. Engrafted lymphocytes mainly damage bone marrow causing bone marrow failure because of severe hypoplasia.
  • Presents with fever, rash, diarrhea, liver dysfunction and bone marrow failure, which are usually seen 1-6 weeks following transfusion.
  • Diagnosis is made by VNTR assay of peripheral blood or skin biopsy. FISH can be used in X-Y mismatched transfusions.
  • It is fatal in >90% of patients.
  • Only option of treatment is bone marrow transplant
  • It can be prevented by using irradiated blood. Irradiation eliminates lymphocytes in the blood that is being transfused.
  • In emergency situation, when irradiated blood is not available, older red cells which are stored for >14 days may be used.

Blood component therapy

RBC Transfusion

• Stored at 4-6 degree C.
• Usual hemoglobin trigger for hemodynamically stable patient is 7gm/dL.If patient has coronary artery disease and for surgical patients, trigger is 8gm%.In case of chronic anemia, where diagnosis is made and hemoglobin is expected to increase, trigger for transfusion is 5gm%.
• Volume to be transfused in children  (ml)= Weight in Kg x 15
• In adults 1 unit increases hemoglobin by 1gm%
• If 2 PRBCs are beingtransfused, give frusemide between 2 transfusions.
• Routine premedication is not necessary.
• Stored PRBCs are as good as stored one.
• No need to warm unless more than 3lit blood is transfused continuously.
• 1 unit must be transfused over 2 hrs. Infusion must be slow in initial 30min to observe for any allergic reaction. In children 2.5ml/Kg/hr.
• Do not add any drugs to blood. Even there should not be Y connection with any IV fluids.
• If there are severe allergic reactions, use washed PRBCs.

Platelet transfusion

• Trigger
  • <10,000/cmm- Transfuseprophylactically except patients with 
    • Chronic bone marrow failure that are asymptomatic and not receiving any intensive therapy.
    • Immune thrombocytopenic purpura without serious bleeding.
  • 10,000- 20,000/cmm- Transfuse if there is bleeding/ fever/ sepsis/ splenomegaly/ disorder causing platelet consumption. If there is severe bleeding, this target is 50,000/cmm.
  • For procedures such as bone marrow aspiration/ biopsy, PICC line insertion, traction removal of tunneled CVC, cataract surgery, no platelet transfusion is required.
  • If invasive procedure is planned- Target platelet count is 50,000/cmm
  • For Neuro/ retinal surgery, epidural catheter insertion/ removal- Target is 1,00,000/cmm
  • Any count- Platelet function defect with bleeding not responding to pharmacological agents such as rVIIa/ desmopressin/ tranexamic acid.
• Platelet transfusion is contraindicated in TTP and HIT.
• Stored at 20-24 degree C for 5 days.
• Bags must be continuously agitated during storage and until they are transfused.
• "Swirling" appearance on gross visual inspection indicates viable platelets.
• If same blood group is not available, platelets of any blood group may be used. For RhD negative girls or women of childbearing potential, give RhD negative platelets. If not available RhD positive platelets can be given with Anti-D prophylaxis.
• Dose for adult- 4 RDPs or ½ - 1 SDP
• Pediatric dose- 1RDP/12Kg- Transfuse over 1hr
• Transfusion should be done in 30min
• If platelet count on next day is <20,000/cmm, it indicates platelet refractoriness. Consider clinical causes for platelet refractoriness in such patients. If none are present, give HLA matched platelets. If there is no increment with this give HPA selected platelets.  In spite of this, if there is no increment, transfuse more platelets only if there is active bleeding.
• Cold stored platelets:
  • Stored at 4 degree C without agitation for 3 days
  • Used only for resuscitation of actively bleeding patient
  • Refrigeration activates platelets (Ex: increased P selectin expression) and renders them more immediately efficacious after transfusion
• Causes of platelet refractoriness (assessed by checking platelet count 1 hour after transfusion)
  • Antibodies against platelets- ITP, Anti HPA antibodies, anti-HLA antibodies
  • Splenomegaly
  • Sepsis
  • Active bleeding
  • DIC
  • Veno-occlusive disease
  • Drugs such as Amphotericin

Fresh Frozen Plasma (FFP) transfusion

• Indications
  • INR- >2 with active bleeding/ invasive procedure is planned. Avoid prophylactic use of plasma in non-bleeding patients.
  • Liver disease causing significant defects in coagulation factors
  • Factor deficiency, when specific concentrate is not available
  • Rapid reversal of warfarin effect
  • Severe DIC
  • As replacement fluid in TTP
  • When large amounts of PRBC is being transfused
• 1 unit contains 175-250ml of plasma
• Volume to be transfused each time- 10-15ml/Kg
• Contains all clotting factors.
• Stored at -20 degree C. Once frozen, plasma can be stored up to 36 months. FFP must be transfused as soon as possible after thawing. Thawing is done in water bath or microwave ovens. If transfusion is being delayed then it should be stored at 1-6 degree C.
• No compatibility testing is required.
• Factor VIII is used for quality monitoring as it is one of the most labile factors.

Cryo precipitate

• Contains Factor VIII, von Willebrand factor, Factor XIII, Fibronectin and fibrinogen.
• Stored at -20 degree C.
• Indications
  • Severe DIC with bleeding
  • Fibrinogen- <100mg/dL
  • Uremic bleeding
  • Hemophilia A
  • VWD
  • Hemorrhage after cardiac surgery
• Monitor- PT, APTT and Fibrinogen
• Dose: 1bag/10Kg
• Transfuse over 1 hour

Granulocyte transfusion

• Usually granulocytes of same blood group are given.
• Avoid multiparous woman as donor.
• 12 hrs prior to collection single dose of G-CSF or Dexamthasone 8mg is given.
• Methods of preparation
  • Apheresis from donor (With/ without GCSF stimulation)
  • Pooling of buffy coats, from whole blood donations
• Transfusion should be done within 6hrs of collection
• Indications
  • Prophylaxis in patients with history of severe fungal infection, prior to HSCT.
  • As therapy in patients who develop infections during post transplant period and do not respond to appropriate antibiotic- antifungal therapy
• Its role in decreasing mortality is still inconclusive.

Leucodepleted products:

• Removes granulocytes and prevents alloimmunization to HLA- Class 1 antigens. 
• Advantages include:
  • Decreases febrile reactions
  • Decreases HLA alloimmunization, hence decreases chances of graft failure after Haplo/ MUD transplant and decreases platelet refractoriness.
  • Decreases chances of CMV infection
• Pre-storageleucodepletion is better than bedside filtration.

Irradiated blood products:

• Useful in preventing transfusion associated GVHD.
• For irradiation, Gamma or X ray (25Gy) is given to all parts of blood component bag.
• Whole blood, PRBC, platelets and granulocytes need to be irradiated. There is no need to irradiate plasma or cryoprecipitate.
• Indications
  • Autologous HSCT- Up to 3 months post transplant
  • Allogeneic HSCT- Until immunosuppression is stopped, patient is free from active chronic GVHD and lymphocyte count is >1,000/cmm. If fludarabine is used during conditioning, irradiation of blood products is needed for the lifetime of patient.
  • Patients with congenital immunodeficiency syndromes
  • Fetus (intrauterine transfusions) and premature neonates.
  • Patients with hematological malignancies especially Hodgkin’s lymphoma
  • Aplastic anemia patients receiving ATG
  • Patients receiving Alemtuzumab and purine analogues (Fludarabine/ Cladribine/ Pentostatin).
  • If blood from close relative is being transfused.
• Leucodepletion/ washing RBCs do not provide protection against TA-GVHD.
• Irradiated blood products must be identified by appropriate label which are sensitive to irradiation. These labels change the color after proper irradiation.
• File of patients who require irradiated products must be labeled with stickers indicating the same.

Washed PRBC

• Indicated in patients with history of anaphylaxis/ severe allergic transfusion reactions.

Massive bleeding protocol:

• It is any bleeding that leads to heart rate of >110BPM and/or systolic BP of <90mmHg.
• Causes include-Trauma, GI bleed, Cardiac/ other major surgeries and PPH
• Every hospital must develop their protocol for providing blood on emergency basis and other management of bleeding patient, to avoid unacceptable morbidity and mortality. This requires a team work involving emergency medicine, blood bank, laboratory, haematologist, anaesthetist/ intensive care unit, interventional radiologist and clinicians based on clinical area.
• Steps in managing
  • Advanced Life Support principles
    • Insert wide bore peripheral or central canula
    • Give pre-warmed crystalloid or colloid as needed
    • Avoid hypotension or urine output <0.5ml/kg/h
    • Monitor central venous pressure
    • Keep patient warm
    • Concealed blood loss is often underestimated
  • Local control of bleeding 
    • Should be done by appropriate experts such as vascular/ general/ cardiothoracic surgeon, endoscopist, gynaecologist etc. 
    • Early referral is must
    • Radiological embolization is an option
  • Haemostatic measures including transfusion support 
    • PT, PTT, Fibrinogen and hemogram should be tested every 30-60min depending on severity of blood loss
    • Tranexamic acid- 1gm- TID
    • Initially give FFP: RBC in 1:1 Ratio. May give O negative blood, till cross match is done. For men O positive blood can be used. Use group specific RBCs as soon as available. Blood warmer may be used to prevent hypothermia.
    • Rapid infusion (Ex: 1 PRBC over 5-10 min) is needed.
    • Cell salvage may be used in cardiac, obstetric, trauma and vascular cases.
    • Once lab parameters are available maintain following targets
      • Hemoglobin- Usually 7-9gm/dL (Give PRBCs irrespective of Hb values, if patient is continuously bleeding/ hemodynamically unstable, as it takes some time for Hb to fall in case of acute blood loss)
      • Platelet count- 50,000/cmm
      • Fibrinogen- 1.5gm/dL
      • PT/PTT- <1.5X Normal
    • Continue giving appropriate blood components until bleeding ceases.
    • Thromboprophylaxis must be started as soon as possible after bleeding ceases.

Recent advances:

iPLAT1: the first-in-human clinical trial of iPSC-derived platelets

Alloimmune platelet transfusion refractoriness is a serious clinical issue present in 5% to 15% of patients who undergo platelet transfusion owing to sensitization against alloantigens such as HLA class I and human platelet antigens (HPAs). In the present study, researchers developed an induced pluripotent stem cell–derived platelet product. This clinical trial of an autologous transfusion of patient-derived iPSC-PLTs, the iPLAT1 study, was approved by Kyoto University. The study suggested significant improvements in the efficacy and cost of producing iPSC-PLTs could realize the practical personalized medicine of autologous platelet products, which are essentially nonrejectable. 

https://doi.org/10.1182/blood.2022017296

Inhibition of GPIb-α-mediated apoptosis signaling enables cold storage of platelets 

The study investigated the impact of apoptosis inhibition on the hemostatic functions and survival of cold-stored platelets (CSP). Inhibition of the apoptotic signal induced by glycoprotein Ib (GPIb)-α clustering, using a RhoA inhibitor, improved δ granule release, platelet aggregation, adhesion, and clot stability compared to untreated CSP. Upregulation of protein kinase A, however, led to impaired platelet functions. Importantly, inhibition of the intracellular signal induced by GPIb-α clustering improved the half-life of CSP, suggesting that combining cold storage with apoptosis inhibition could be a promising strategy to prolong storage time without compromising hemostatic functions or platelet survival. 

https://doi.org/10.3324/haematol.2022.282572