Platelets/HLA

Question 1

True or False: In alloimmune refractory patients, the best increments occur in the subset of Grade A and BIU or or B1X HLA-matched transfusions.

Answer 1

False: Grade A and B1U or B@U HLA-matched

Question 2

True or False: HLA-matched platelets should be irradiated to prevent transfusion-associated graft-vs-host disease.

Answer 2

True

Question 3

What are some causes for non-immune platelet refractoriness?

Answer 3

Sepsis
Fever
DIC
Massive bleeding
Splenomegaly
Chemo or radiation
Drugs like amphotericin B
TTP
Liver dysfunction

Question 4

True or False: Fetal or Neonatal Alloimmune Thrombocytopenia (FNAIT) like HDFN occurs during the first pregnancy and then affects subsequent pregnancies.

Answer 4

False: FNAIT affects the first pregnancy

Question 5

What is the most commonly implicated platelet antigen in FNAIT?

Answer 5

HPA-1a (but all HPA antigens have been implicated)

Question 6

What is the treatment for thrombocytopenia newborns w/ FNAIT?

Answer 6

IVIG + maternal washed platelets (if antigen compatible)

Question 7

Name four drugs commonly implicated in drug induced thrombocytopenia.

Answer 7

Heparin
Vancomycin
Quinine
Sulfa drugs
GPIIb/IIIb antagonists

Question 8

Name three characteristics of Heparin Induced Thrombocytopenia characteristics

Answer 8

Occurs within 5-14 days after primary exposure
>50 % develop thrombosis
Associated with a 30-50% reduction in platelet count from pre-dose baseline

Question 9

Discuss characteristics of Immune Thrombocytopenia (ITP)

Answer 9

Formerly idiopathic thrombocytopenia
Autoantibodies of multiple classes (IgG, IgM and IgA)
Acute-mainly in childhood often following viral infection/abrupt onset/majority resolve over 2-6 months
Chronic-mainly in adults; less likely to spontaneously resolve
May be idiopathic or occur w/ other conditions (HIV, malignancy, autoimmune diseases)

Treatment-IVIG or RhIg, steroids,rituximab and rarely splenectomy

Question 10

Name three immune neutrophil disorders

Answer 10

NAN
TRALI
AIN

Question 11

Describe the characteristics of Neonatal alloimmune neutropenia

Answer 11

Caused by maternal antibodies against fetal neutrophil antigens
Most commonly directed at HNA-1a, HNA-1b and HNA-2
Neutropenia is usually self-limiting (but can predispose to life-threatening infection)
Management options include: antibiotics, IVIG, G-CSF and plasma exchange

Question 12

Describe characteristics of Autoimmune Neutropenia (AIN)

Answer 12

May occur in adults or infants

In adults-
idiopathic or secondary to underlying conditions (RA, SLE or bacterial infections)

In infants-
typically between 6 months-2 years
specificity usually in HNA-1a or 1b)
Spontaneous remission is common
Manageable with antibiotics

Question 13

Describe four key roles played by HLA molecules

Answer 13

Antigen presentation and initiation of immune response
Recognition of self/non-self
Relationship/forensic testing
Transfusion and transplantation

Question 14

Where are HLA Class I and Class II antigens found?

Answer 14

HLA Class I-found on platelets and most uncleared cells of the body
HLA Class II-found on antigen-presenting cells, including B lymphocytes, monocytes, macrophages, dendritic cells, activated T lymphocytes, intestinal epithelial cells, early hematopoietic cells and some endothelial cells lining the microvasculature

Question 15

HLA Disease Associations

Answer 15

Celiac disease-DQ2
Ankylosing spondylitis-B27
Narcolepsy-DQ6
Subacute thyroditis-B35
Type 1 diabetes-DQ8
Multiple Schlerosis-DR15, DQ6
Rheumatoid arthritis-DR4