Immune system is a part of organism and develops in accordance with organism i.e. for the period of childhood up to the age of fifteen, puberty age. A number of lymphocyte clones accumulated by the age of 15 is further maintained by "background" proliferation and is being spent during productive immune responses to pathogens penetrating internal environment. Generation of new lymphocyte clones is impossible in adult organisms. The latter was testified by impossible reconstitution of diverse repertoire of antigen-presenting Rc, and sometimes of large lymphocyte number eliminated due to irradiation, lymphotropic viral infections, etc.). In other words followed their amputations in some way or other lymphocytes fail to grow again (a new foot is unable to grow in the place of amputated one alike to any parenchymatous organ).
The fact that each lymphocyte is programmed for clone proliferation in immune response does not mean life-long plenum of lymphopoiesis potential: it is restricted by the age of 15. And so there exist acquired or secondary immune deficiencies (SID).
• If in post-natal period a healthy organism with healthy immune system had been exposed to pathogenic effects which physically damage large lymphocyte quantities a secondary immune deficiency occur.
• Due to certain systemic pathologic states functional "paresis" of immune system occurs rather than physical elimination of lymphocytes. Such states are referred to SID. In contrast to SID with physical lymphocyte defects functional "paresis" of immune system or its dysfunction is reversible in case that causal disease is curable and did not develop very long.
Immune system examination conducted in case of suspected SID suggests to determine a number of peripheral blood indices similar to those determined for suspected innate immune deficiencies such as HIV-infection, hemogram, blood serum IgG, IgA, and IgM; skin samples for DTH to common microbial Ag, if needed T-and B-lymphocyte subpopulation count; for specific indications - phagocytosis state (the most simple and informative test - tetrazolium blue); for specific clinical indications - complement components contents (to begin with C3 and C4) and other tests (due to clinical symptoms).