Immune Mediated Anemia

Question 1

What are agglutinated RBCs

Answer 1

Clumping of RBCs due to antibodies

Question 2

What is a test for this

Answer 2

Antiglobulin test or the Coomb’s test. There are 2 types of this test: Direct test: If we look at RBCs, are there antibodies on them. This is detected by Coomb’s reagent which is an antibody against the RBC antibody. Indirect test: Are there antibodies in the serum that have the ability to bind to RBCs. Also checked with Coomb’s reagent. In both of these tests we check for agglutination.

Question 3

What is different types of agglutination

Answer 3

Warm and cold. 1. IgG causes agglutination in warm temperature whereas IgM causes cold agglutination. 2. Few patients have mixed - SLE 3. Chronic inflammation and neoplasm induces warm agglutination 4. Mycoplasm and B cell lymphoma disorders induce cold agglutination

Question 4

Answer 4

E

ABO are saccharides, so there has to be a T independent response, the most common T independent antibodies are IgM

Question 5

Patient presents with fever after receiving chemotherapy 3 weeks ago. The patient is neutropenic and thrombocytopenic, blood trasnfusion is then given to the patient. Patient’s condition worsens after the trasnfusion. What is the answer to this

What about the indirect agglutination test? Would it be positive as well?

Answer 5

Positive, since the patient makes antibodies against the foreign blood but those antibodies also attack his own RBCs.

Indirect would also be positive

Question 6

Expalin the process step by step what happened in this patient after the mismatched transfusion took place

Answer 6

1. IgMs are made against the RBCs, they bind to the RBCs
2. Compliment system is activated, C1q binds to the IgM which is in turn bound to RBC
3. C3a and C3b combine to form convertase and ultimately C5
4. This will lead to inflammation and recruiting neutrophils, activation of mast cells
5. With inflammation comes: vasodilation, vascular peramibility, drop in blood pressure
6. RBCs lyse and release their contents which are toxic to kidney. Kidneys get uncomfortable, causing backache.
7. Patients are given a lot of fluids to reduce kidney damage

Question 7

Answer 7

IgG

Question 8

Answer 8

Neonatal Fc receptor

Answer is D.

Remember the 2 exceptions when a receptor can bind to a free antibody (antibody not bound to a microbe): 1. IgE binding to Fcepsiolon receptor on mast cells 2. Neonatal Fc receptor binding to IgG

Question 9

Answer 9

There is an important concept here to know: Since the antibody is IgG there has to be class switching which means it was a T cell mediated immune response. Since T cells only detect proteins, IgG then have a higher affinity for proteins than any other class of molecules

Question 10

What kind of antigen is the Rh and what genes are associated with it

Answer 10

It is a protein antigen, genes involved are the D gene and CE gene. However D gene is more immunogenic so when we say Rh negative or positive we refer to the fact that it is RhD positive or negative

Question 11

Patient diagnosed with drug induced hemolytic anemia. What would his direct and indirect antiglobulin test would be

Answer 11

Direct will be positive and indirect will be negative since this is a drug induced hemolytic anemia so no antibodies are there against the RBCs

Question 12

Three scenarios of hemolytic anemia that we talked about and when is the direct and indirect antiglobulin test positive and negative and what is the rationale behind it

Answer 12