Correspondence: Toshinori Komatsu

NORIATU SAEKl
TOSHINORI KOMATSU
ITUJI SAKAMOTO
TAKAO FUNATO
KENJI 'NAKANISHl
Department of Immunology and Medical Zoology, Hyogo College of Medicine, 1-1, Mukogawa-cho, Nishinomiya, Hyogo, 663 Japan.

Abstract
Heated (56 'C, 45 min; HGPS), but unheated guinea pig serum (NGPS) exhibited trypanocidal activity in the presence of an ultrafiltrate of fetal bovine serum (nominal molecular weight < 3000; FBS component). The activity caused cell swelling and finally lysed trypanosomes, presumably by osmotic pressure. HGPS also generated the activity in the presence of L- or D-cysteine, but in different manner. The trypanocidal activity of HGPS depended on the concentration of the FBS component but not simply upon that of cysteine. It appeared to be generated by cysteine concentrations that counterbalanced that of the HGPS. Saturating NGPS with 40% ammonium sulfate revealed two factors. One precipitated by the ammonium sulfate exhibited trypanocidal activity in the presence of FBS component or cysteine only when heated. The other in the ammonium sulfate-unprecipitable fraction exhibited trypanocidal activity only in the presence of cysteine, regardless of heating. L-cysteine methyl ester, L-cysteine ethyl ester, S-methyl-L-cysteine and glutathione had no effects on the generation of the trypanocidal activity of HGPS. On the other hand, bovine serum albumin (BSA) exerted trypanocidal activity when L-cysteine, but not FBS component, was present. In contrast to HGPS, BSA exhibited the activity in the presence of L-cysteine methyl ester or L-cysteine ethyl ester.