Platelet and Granulocyte Antigens and Antibodies Flashcards
how does expression of ABO antigens on platelets occur?
adsorption from plasma and material that is intrinsic to surface membrane of the platelet
where are HLA antigens found?
nucleated cells
platelets are part of what HLA class?
class I
what HLA antigens are associated with platelets
HLA-A and HLA-B
what is responsible for primary HLA alloimmunization in patients who have been transfused platelets?
residual white cells
how long after platelet transfusion is platelet response measured?
10-60 minutes
what defines a platelet refractory state?
post-transfusion CCI of <5000-7500 following 2 consecutive platelet transfusions
most common immune cause of platelet refractoriness
HLA sensitization
nonimmune-related reasons for recipient platelet refractoriness
massive bleeding, fever, sepsis, splenomegaly, DIC, allogeneic transplant, drugs, TTP
how is HLA sensitization diagnosed
microlymphocytotoxicity testing
corrected count increment calculation
(BSA x plt ct increment) / number of platelets transfused
post-transfusion platelet recovery calculation
(total blood volume x plt ct increment) / number of plts transfused
total blood volume estimate in adult patients
75 ml/kg
expected platelet count increase from platelet concentrate
5,000-10,000
expected platelet count increase from apheresis platelet
30,000-60,000
transfusion requirement for HLA-matched platelets
irradiation to prevent GVHD
transfusion options for platelet refractoriness
crossmatched platelets
HLA-matched platelets
antibody specificity prediction
most widely used method for platelet crossmatching
solid-phase red cell adherence
5 platelet specific antigens characterized as alloimmunogenic and polymorphic
GPIa, -Ib, -IIb, -IIIa, CD109
alternative approach to HLA-matched and crossmatched platelets determining recipient’s HLA antibody specificity and then selecting platelet donors who lack antigens to antibodies produced by the recipient
antibody specificity prediction
prevention of HLA alloimmunization from platelet transfusion
leukocyte reduction
UVB irradiation
HPA-1a antigen frequency
98% of white population
most commonly encountered platelet-specific antibody identified in white population
anti-HPA-1a
HPA-1b platelet antigen frequency
27% of white population
location of HPA-1a and HPA-1b
GP111a platelet membrane glycoprotein
disease state in which patients lack GP111a glycoprotein and don’t express HPA-1 antigens
Glanzmann thrombasthenia type 1
major complication of neonatal alloimmune thrombocytopenia
major bleeding that can lead to intracranial hemorrhage
confirmation test to diagnose neonatal alloimmune thrombocytopenia
platelet-specific antibody within maternal serum and corresponding incompatibility for the antigen in parental platelet types
treatment of neonatal alloimmune thrombocytopenia
IVIG with or without compatible platelet transfusions
most common platelet antigen incompatibility in neonatal autoimmune thrombocytopenia
HPA-1a
identified when patient experiences sudden, dramatic, self-limiting form of thrombocytopenia ~5-10 days after blood transfusion coinciding with potent platelet-specific alloantibody
posttransfusion purpura
treatment of posttransfusion purpura
IVIG
diagnosis of posttransfusion purpura
genotyping and platelet antibody assays
platelet antibody detection method type: assays mixing patient serum with normal platelets using platelet function-dependent endpoints
phase I
platelet antibody detection method types: measures surface or total platelet-associated immunoglobulin
phase II
platelet antibody detection method types: solid-phase assays, binding of antibodies to isolated platelet surface glycoproteins
phase III
platelet antibody detection assay in which intact platelets are immobilized in round-bottom wells of microtiter tray, incubated with patient’s serum, washed, antibody specific coated red cells added, incubate, centrifuge, visually examine
mixed passive hemagglutination assay
drawback of mixed passive hemagglutination assay platelet antibody detection
fails to distinguish non-platelet-specific from platelet-specific antibodies
mixed passive hemagglutination assay is phase _ type of platelet antibody testing
I
flow cytometry is phase __ type of platelet antibody detection
II
platelet antibody detection assay often used for platelet crossmatching using immunofluorescence
flow cytometry
monoclonal antibody-specific immobilization of platelet antigen assay is phase ___ type of platelet antibody detection
III
platelet antibody detection method that requires use of murine monoclonal antibodies that can recognize target antigens
monoclonal antibody-specific immobilization of platelet antigen
chronic immune thrombocytopenia usually seen in what patient population?
adults
first line therapy for chronic ITP
steroids or IVIG
autoantibodies directed against platelet antigens could result in what pathological conditions?
immune thrombocytopenia or immune thrombocytopenic purpura
acute IPT usually seen in what patient population
kids
first line therapy for acute ITP
IVIG or anti-D immunoglobulin infusions given to D-positive patients
platelet autoantibody classes
IgG, IgM, IgA
complication of drug therapy in treatment for platelet autoantibodies
thrombocytopenia caused by drug-induced platelet antibodies
common drugs associated with drug-induced thrombocytopenia
quinine/quinidine, sulfa, heparin, colloidal-gold
testing for drug-dependent platelet antibodies
flow cytometry, SPRCA assay
drug-induced immune response to platelets triggered by widespread use of heparin
heparin-induced thrombocytopenia
clinical syndromes that implicate antibodies against neutrophil antigens
neonatal alloimmune neutropenia
TRALI
immune neutropenia after HPC transplant
refractoriness to granulocyte transfusion
chronic benign autoimmune neutropenia or infancy
implemented by maternal antibodies against antigens on fetal granulocytes
neonatal alloimmune neutropenia
antigens associated with neonatal alloimmune neutropenia
HNA-1a, HNA-1b, HNA-2a
treatment of neonatal alloimmune neutropenia
antibiotics, plasma exchange, IVIG, granulocyte colony-stimulating growth factor
characteristic symptoms of TRALI
hypo or hypertension, respiratory distress, noncardiogenic pulmonary edema
TRALI commonly seen within 2 hours of what blood component
plasma-containing components
TRALI brought on by antibodies towards what?
granulocyte-specific antigens or antibodies to HLA antigens
autoantibody implicated in autoimmune neutropenia
HNA-1a or HNA-1b
testing for granulocyte antibodies
combination of agglutination and immunofluoresence
