Clinical immunology

 Question 1

Please could you explain how lymphocytes (especially B) can maintain receptors on their surfaces? Is this genetically related? If so, when the lymphocytes are first exposed to the antigens, how could the antigen receptor be synthesized? Is there a mutation within the nuclei of these lymphocytes when they learn to make the receptors? If there is, can you explain how this occurs?

Answer 1

B cells differentiate from lymphoid cells within the bone marrow during a way that allows them to express an antigen receptor on the surface permanently. The expression of the receptor is a definition of B cells and is a result of the differentiation pathway. The antigen receptor varies from one immature B cell to another. There are billions of different receptors, but any B cell will express just one sort of receptor.

The antigen does not ‘design’ the receptor; rather, a clonal B cell that recognizes the antigen (very few B cells will recognize a given antigen) will proliferate in response to the antigen and signals from T cells.

As the B cells proliferate and differentiate further, the DNA region that codes for the antigen receptor undergoes mutation, and cells with mutations that recognize the antigen better are selected for further development, while those that do not recognize the antigen die.

Question 2

I understand how nuclear factor-κB (NFκB) works in the inflammatory response but what is the mechanism by which it causes cancer?

Answer 2:-

NFκB is a transcription factor that alters cell behaviour. It inhibits apoptosis and increases cell proliferation by increasing the assembly of tumour necrosis factor (TNF-α).

Question 3

What are the diseases associated with hypocomplementaemia and which complement deficiency in particular?

Answer 3:- 

The following are the major patterns of deficiency:

● C3, C1q and factors H and I: susceptibility to capsulated bacteria, also systemic lupus erythematosus (SLE)-like syndrome

● C5-9: susceptibility to disseminated neisserial infections

● C1 esterase deficiency: hereditary angio-oedema.

Question 4

What is meant by ‘B lymphocytes are sensitive to clonal deletion’?

Answer 4:- 

Clonal deletion occurs during the event of immune tolerance.Clonal deletion occurs when lymphocytes of a particular specificity are lost when in touch with ‘self’ or an extrinsic antigen.

Question 5

What are the immunological implications of ‘bare lymphocyte syndrome’/MHC deficiency?

Answer 5:- 

In the bare lymphocyte syndrome, a rare recessive condition, major histocompatibility complexes are not expressed. The clinical manifestation is of severe combined immune deficiency (SCID). Patients present in infancy with viral, bacterial, fungal and protozoal infections that are difficult to regulate due to poor immunity.