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Serum and neutrophils alter the rate of excretory/secretory antigen release by Toxocara canis infective larvae in vitro

Summary Infective larvae of Toxocara canis are well suited for studies of nematode antigen expression in vitro. Larvae were labelled with 3H‐glucosamine, an approach permitting dual analysis of antigen quantity and composition. Their excretory/secretory (E/S) glycoproteins were efficiently labelled and antigen identity confirmed by immunoprecipitation, SDS‐PAGE and fluorography. Compartmental analysis revealed that common components of Mr 100–120 kD were present in somatic, surface and soluble material. The application of biosynthetic labelling and compartmental analysis of parasite responses in vitro to antibody, complement and neutrophils was tested. Results indicated that test larvae in vitro respond by quantitative rather than qualitative changes in antigen production. Specifically, human serum was shown to raise, and neutrophils depress, the rate of antigen release. The implications of these findings for establishing an in‐vitro model for analysis of host/parasite reciprocal adaptive responses are discussed.