Changes in the flow and composition of gastric lymph in sheep repeatedly infected with Ostertagia circumcincta

Abstract

A technique is described for catheterizing the gastric lymph duct of sheep, together with a reinfusion apparatus which continuously samples the lymph. The flow and composition of lymph sampled from 9 worm-free sheep was compared with that of 6 sheep which had been repeatedly dosed with Ostertagia larvae and which were showing signs of resistance to reinfection. Lymph flow was increased almost 2-fold in the infected sheep, and although the concentrations of IgG and IgM were similar in both groups, the amount of IgA was significantly raised in the immune animals. The lymph:serum ratios for IgA, IgG and IgM were 2·69, 0·59 and 0·17, respectively, indicating that the bulk of IgA was locally produced. The rate of output of IgA was about 5 times higher in the infected group. Radioimmunoassays revealed large amounts of IgA and IgG anti-larval antibody in the immune lymph but IgM from both groups was bound to the antigen. Total lymphocyte output was about 1·5 times greater in the lymph of the infected sheep but the output of large cells was unchanged. IgA was the predominant type of immunoglobulin-containing cell in all sheep and the rate of output of these cells was raised about 9 fold in the infected animals. IgM- and IgG-containing cells were always relatively rare (<0·5 per cent) although between 10 and 30 per cent of cells from both groups stained for surface IgM. No specific stimulation was detected with a range of concentrations of larval antigens in a sensitive lymphocyte transformation test.