In regulation of specific immune responses the most important role play interleukin-2, IL-4, IL-5, IL-13, inter feron- (INF- ), transforming growth factor- (TGF- ) and lymphotoxin (LT). These signal molecules are produced mainly by T-lymphocytes after recognition of foreign antigens by specific receptors (TCR) placed on plasmalema. Some of mentioned cytokines stimulate proliferation and differentiation of various lymphocyte populations in the activation phase of T cell-de pendent immune responses, while the others activate and regulate the function of specialized effector cells, such as mono nuclear phagocytes, eosinophils, and neutrophils, to eliminate antigens in the effector phase of immune responses. In con trast to most of cytokines which have stimulating action on an initiation and course of humoral and cell-mediated immune responses, TGF- has an inhibitory effect on the activation and proliferation of T-lymphocytes and the other leukocyts

The complement system (complement) involves over 30 circulating and membrane-fixed proteins with an effector
role in the innate and humoral immunity. These proteins help the function of antibodies to protect the organism from foreign
molecules (antigens) which the term complement comes from. Soluble proteins of the complement system made mainly in
the liver and circulate in blood in an inactive form. The activation of complement may be initiated in three ways (classical,
alternative and lecitin pathway), and it is realized by sequential proteolysis of complement proteins (proenzymes) which
become emzymes with the proteolitic activity after cleavage. Products of the activatin of complement bind to the surface of
microbes or to the antibodies bound to antigens. An activated complement shows a number of biological effects, such as
lysis of an attached cell, opsonization, neutralization of viruses, inflammation, clearance of immune complexes etc. In contrast of microorganisms, human cells have a number of regulatory proteins which prevent the complement activation and in that way, they regulate its activity