Abstract
Specific immune mechanisms are divided into humoral which are mediated by antibodies and cellular, which are mediated by T lymphocytes. T and B cells have on their surface antigen-specific receptors which recognize antigens fine details.
A characteristic feature of the specific immune mechanisms is immunological memory, which is mediated by memory T and B cells. T cells do not recognize native antigens via their TCR, but recognize only complexes of antigen fragments bound to the HLA molecules on the cell surface.
For T cell activation is necessary contact with a suitable APC. T lymphocytes are divided into several subpopulations which differ in their function and some surface features, the most important are TH1, TH2, and Tc lymphocytes.
TH1 lymphocytes activate macrophages and TH2 lymphocytes stimulate B cells and helping in antibodies production. Cytotoxic T lymphocytes are able to kill cells infected by viruses or other intracellular pathogens or tumor cells.