Assays For Immune function

Question 1

What initial screening lab should be considered first?

Answer 1

CBC w/diff (tests for number of cells)

Question 2

What are the examples of other initial screening labs?

Answer 2

1. Inflammatory Markers
   - Erythrocyte sedimentation rate
   - CRP (which activate complement system)
2. Chemistry Panel
   - Urinalysis to check liver and kidney for protein loss

Question 3

What diagnostic testings are to be considered if not sure B or T cell immunodeficiency?

Answer 3

1. CBC w/diff
2. Lymphocyte Markers (Flow cytometry)
3. Serum IgG, IgA, IgM

Further tests to consider if B Cell deficiency:
- Antibody Function Test: Titer to vaccine/isohemagglutinins

Further tests to consider if T Cell deficiency:

• In Vitro T Cell Function Test: Mitogen Proliferation Test
• In Vivo T Cell Function Tet: Delayed Type Hypersensitivity

Question 4

What else can be considered if Igs are all low?

Answer 4

Protein Loss

Question 5

What is the lymphocyte marker of T cells?

Answer 5

CD3

Question 6

What is the lymphocyte marker of helper T cells?

Answer 6

CD4

Question 7

What is the lymphocyte marker of Cytotoxic T cells (and 1/3 NK cells)?

Answer 7

CD8

Question 8

What is the lymphocyte marker of B cells?

Answer 8

CD19

Question 9

What is the lymphocyte marker of NK cells (2/3)

Answer 9

CD16/CD56

Question 10

What lymphocyte markers are tested by Limited testing?

Answer 10

CD 3,4,8

Question 11

What lymphocyte markers are tested by complete testing?

Answer 11

All lymphyocyte markers we have to know

Question 12

What is flow cytometry?

Answer 12

Technology assay that uses fluidics, optics, and electronics to provide rapid assessment on cell by cell basis.

Question 13

Describe Monoclonal Antibodies

Answer 13

Monoclonal antibodies are man-made laboratory proteins that act like human antibodies in the immune system.

Question 14

Describe Fetal Hemoglobin Testing

Answer 14

The purpose of this test is to determine if the mother has experienced a placental bleed which would allow fetal blood cells to enter maternal circulation. This test is particularly important when an Rh negative mother has an Rh positive fetus.

Question 15

What is mitogens testing?

Answer 15

It’s an in vitro T cell function test that measures the T cell mitosis/proliferation by measuring the radioactivity taken up by the t cells in vitro.

• Low radioactivity = abnormal

Question 16

What is Delayed-Type Hypersensitivity Testing (DTH)?

Answer 16

In VIVO test of intradermal injection of antigen to see the response.

• Example: PPD or TB skin test

Question 17

What steps are necessary to evaluate neutrophil defects?

Answer 17

1. CBC w/diff
2. If related to neutrophilia or neutropenia, find etiology (we learned several)
   - congenital neutropenia
   - LAD
   - response to recent infection or antibiotics
3. If neutrophil numbers are normal, test the function of neutrophils
   - CGD (NBT or flow cytometry)
   - Hyper IgE syndrome (serum IgE)
   - Chediak-Higashi syndrome (giant azurophilic granules)

Question 18

What steps are necessary to evaluate complement defects?

Answer 18

1. CH50 (assessment of classical pathway)
   - If reduced, specific complement components can be assessed.
2. If CH 50 is normal, AH50 (assessment of alternative pathway)
   - Can be due to properdin and factor D deficiencies (rare)