Question

explain how CD8, CD4 and B cells work together either in the lymphoid tissue OR at the site of infection.

Answer 1

T cells and B cells are lymphocytes which are the type of White Blood cells responsible for immunity. B cells and T cells both born in bone marrow but B cells mature in bone marrow whereas T cells travel from bone marrow to thymus gland and mature here, hence the name. CD is a Cluster of Differentiation. T cells have Toll-like receptors (TLRs) on their surface and B cells have B cell receptors (BCRs) which helps in binding.

CD4+ is a Helper T cell when during infection binds to an antigen expressed by Antigen Presenting Cell (APC) and fitted in the groove of  MHC (Major Histocompatibility Complex) 2 molecule.

Now CD4+ is a T Helper cell and has Toll-like receptors that are identical over its surface and are responsible for two types of immunity.

1. Cell-mediated immunity:

Here CD4+ binds to an antigen expressed by APC and in MHC 2 and secretes lymphokines which attract other immune cells the site of infection and release cytokines which leads to inflammation, seen as a rash(redness) or pus formation ( accumulation of white blood cells more specifically lymphocytes at the site of infection), sometimes leading to inflammation causing fever. It binds to the Toll-like receptor on CD8 molecule and activates it which is a Cytotoxic T cell that inturns secrete Perforin and Granzymes. Perforins create pores in the antigen membrane wall and destroy it completely.

Also, when there is any viral infection, the viral antigen is identified by APC cells or macrophage or a dendritic cell and is expressed on MHC1 molecule so that CD8+ Toll-like receptors should identify and bind to the viral antigen and secrete perforins to kill them, and stimulate differentiation of a clone of T cells and memory cells that helps in the same process.

2. Antibody-mediated immunity:

Now. the CD4 or the helper T cell binds to B cell receptor (BCR) on the B cells and stimulates the formation of a clone of plasma cells which in turn will secrete antibodies to effect on the infecting pathogen and a clone of memory B cells.

CD4 stimulates CD8 and B cells and further activates them.

Thus, the CD4, CD8 and B cells or the immunity mediated by cells and antibody works together in harmony and co-ordination to get rid of a pathogen at the site of infection.

I hope this answer helps you!

Best Regards!!