| Popis: |
In recent years, the notion has become generally accepted that the highly antigen-specific immune reactions which take place after the introduction of an antigen into an immunocompetent organism either are enhanced by or even critically depend on the participation of non-antigen-specific molecules. The immunologically relevant non-anti-gen-specific molecules are elaborated either by monocytes (monokines) or by lymphocytes (lymphokines). The most prominent and most thoroughly investigated member of the monokines is LAF (lymphocyte-activating factor; for review see Oppenheim et al. 1979 and Smith et al. 1979), recently also called Interleukin 1. LAF in turn renders a sub-population of T cells, in the mouse predominantly but not exclusively the Thy l+Lytl+2−; helper T cells (Wagner and Rollinghoff1978, Henney et al. 1980), capable of releasing a number of biologically active molecules, provided the T helper cell also sees its relevant antigen or lectin under appropriate conditions (Smith et al. 1979, Larsson et al. 1980). Some of the lymphokines seem to act by maintaining growth of lymphocyte subpopulations, others by inducing a quantal step of differentiation in such cells. An important rule which has emerged, however, is that the lymphocyte targets responding to the factors must have seen the antigens relevant to them by virtue of their antigen-specific receptors in order to be able to respond to the non-antigen-specific lymphokines. Normally the specificity of the immune system is thus maintained at two levels: first, only those helper cells which see their relevant antigen under appropriate conditions produce lymphokines and secondly, only lymphocytes seeing their relevant antigens under conditions appropriate to them can become target cells by developing receptors which enable them to interact with the lymphokine and receive whatever signal is mediated by it. |
