Highly purified pneumolysin (at a concentration of 10 ,ug/ml) caused significant activation of human complement, as measured by conversion of C3. Complement activation in the presence of pneumolysin was not observed in sera chelated with a combination of Mg2' and ethylene glycol-bis(P-aminoethyl ether)-N,N-This work was supported by grants from the National Health and Medical Research Council and the Adelaide Children's Hospital Research Trust. LITERATURE CITED 1. Bradford, M. M. 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein using the princi

Immunization with two doses of live Naegleria fowleri produced a survival of 34% of mice compared to 0% in unimmunized controls, whereas multiple doses of live N. fowleri resulted in loss of protective immunity. In contrast, multiple doses of N. fowleri lysate produced a survival of 30%, and multiple doses of N. fowleri culture supernatant produced a survival of 67 to 78%. Fractionation of the culture supernatant by column chromatography showed that all six fractions contained protective antigens, but the best protection occurred from immunization with the high molecular weight fraction (greater than 200,000 daltons).

An experiment was performed which confirmed a previous finding that mice are protected against Naegleria fowleri infection by immunization with amoeba-free supernatant from amoeba cultures. Histological observations suggested that this protection is expressed mainly at the nasal mucosa and possibly results from the combined effects of polymorphonuclear leucocyte-mediated killing of the amoeba and mechanical elimination of the organisms by extensive shedding of necrotic epithelium.

The effects of pneumolysin, a sulfhydryl-activated cytolytic toxin produced by Streptococcus pneumoniae, on the in vitro human lymphocyte response was examined. The toxin, at concentrations of one to five hemolytic units per ml, caused marked inhibition of the response of lymphocytes to concanavalin A, phytohemagglutinin, pokeweed mitogen, and protein A. The response was assessed by measuring both [3HJthymidine incorporation and the ability of lymphocytes to produce immunoglobulins and lymphokine activity. The effects of pneumolysin were irreversible, could be prevented by pretreatment of the toxin with cholesterol, and were not related to a direct cytotoxic effect on the Iymphocytes. Pneumolysin appeared to act at the initiation phase of the immune response and had no effect on lymphocytes committed to DNA synthesis or to the synthesis and secretion of immunoglobulins. Furthermore, pneumolysin-mediated inhibition of the lymphocyte response was not due to the inhibition of binding of mitogens to leukocytes and is likely to be related to effects on membranemediated signals essential for lymphocyte triggering. This may be one means by which pneumolysin plays a role in the pathogenesis of pneumococcal infections.

Human mononuclear leucocytes (MNL) or the adherent fraction (monocytes) produced tumour necrosis factor-alpha (TNF-alpha) (by ELISA) in culture when stimulated with killed Staphylococcus aureus. The bisbenzylisoquinoline alkaloid, tetrandrine inhibited the capacity of MNL and monocytes to produce TNF-alpha at a concentration range of 0.1 to 5 micrograms/ml. Tetrandrine may be potentially useful in the treatment of inflammatory diseases in which TNF-alpha plays a major role.