T cells antigen presentation

Ricin (castor bean) immunotoxin has been developed to attack the CD5 T-cell antigen (present in T-cell and some B-cell malignancies) as well as the interleukin-2 receptor of cancerous tumors. Ne-urobiological applications of ricin involve the study of brain function via lesioning. It is also used as a reagent for pepsin and trypsin, and as a commercial mole killer. Historically, it has been used as a biochemical warfare agent. 

In all these studies, either serum antibody or the plaque-forming response was tested with the exception of IgE, which was tested by a passive cutaneous anaphylaxis test. In none of the experiments was an attempt made to delineate the cell types that may be stimulated by the retinoid. Therefore, we do not know presently whether the drug acts on B cells, T cells, antigen-presenting cells or other cell types. Three different retinoids were employed and it is not known whether any one in particular may be superior to the others for immunostimula-tion because no comparative studies have been done. 

Class IIHLA molecules are expressed on the surface of antigen-presenting cells. They play a key role in presentation of processed linear peptide antigens of at least nine amino acids to T cells. Antigen is bound to the HLA antigen binding cleft formed by the a and 3 chains of the HLA class II molecule. This tri-molecular HLA-antigen complex binds in turn to the variable portion of the T-cell receptor. 

B cells also have impact on T-cell differentiation. B-cell antigen presentation plays an important role at promoting Th2 responses and pathophysiology during allergic disorders. It has been shown that B-cell -/- mice and in mice selectively deficient in MHCII on B cells had decreased Th2 cytokines IL-4 and IL-5 [152]. Also in another study it has been reported that B-cell-derived exosomes can present allergen peptides and activate allergen-specific T cells to proliferate and produce Th2 cytokines IL-5 and IL-13 [42]. 

CDS Defines MHC class I-restricted T cell subset present on NK cells CDIO Known to be common acute leukaemia antigen CDlla Known to be zn a chain of LFA-1 (leucocyte function antigen-1) present on several types of leucocyte and which mediates adhesion CDllc Known to be z complement receptor 4 a chain. 

Causes apoptosis in T and antigen-presenting cells, preventing initial T cell activation ... 

Activation and differentiation of cytotoxic T lymphocytes (CD8+ T cells) (CTLs) require interplay of various cytokines and cells. During the presentation of tumor-specific antigens by antigen-presenting cells (APCs) to helper T cells (CD4+ T cells), cytokines present in the microenvironment control the helper immune response to develop into either a cellular or a humoral response. CD4+ T cells have been classified into Thl and Th2 subsets according to the pattern of cytokines they produce. Thl clones secrete IL-12 and IFN-y, whereas Th2 clones secrete IL-4, IL-5, IL-6 and IL-10. Thl immune response is beneficial for the development of the cellular cytotoxic (CD8) immune response, whereas Th2 immune response is inhibitory to cytotoxic response. IFN-y is a type 1 interferon that also promotes Thl-type anti-tumor immunity, reduces tumor cell growth, and inhibits angiogenesis. 

Helper killer T-cells activated by antigen presenting macrophage (if T-cells recognises presented antigen) i... 

For example, CD3 is present on all T cells and is part of the T cell antigen receptor-complex. CD4 occurs on T helper cells which participate in MHC class Il-mediated reactions. CD8 occurs on cytotoxic killer T cells which carry out MHC class I-mediated reactions. 

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