[Vital fluorochromasia of mikroorganisms using fluorescein-3',6'-diacetate (FDA). II; Communication: The influences of humoral and cellular defence-mechanisms on vitality of Toxoplasma gondii (author's transl)].

Fluorochromization by using the non-fluorescent, but fluorogenic substrate fluorescein-3',6'-diacetate indicates vitality and metabolic activity of extra- and intracellular Toxoplasma gondii. Specific humoral antibody diminishes the metabolism and, therefore, also the fluorochromization of these parasites; Because toxoplasms invade host cells mainly by active penetration, they are found not only in phagocytes but also in lymphocytes and in hepatocytes. In these cells, a further multiplication of parasites occurs. Only well functioning phagocytes are able to destroy the parasites; This process is supported by humoral antibody. Using IFT, the binding of humoral antibody to vital and killed toxoplasms in phagocytes of peritoneal exudate and spleen can be demonstrated in vivo and in vitro. The destroying effect of humoral antibody is limited by the rapid penetration of toxoplasms into the host cells. After infection, only an early administration of a high dose of antiserum will achieve a sufficient binding of antibodies to be able to influence the metabolism of toxoplasms. Due to this fact and according to the risk of a repression of humoral defence mechanisms in the host by IgG-antibodies the value of passive immunisation is limited.