The antibody-containing cell response of the lamina propria of the sheep and the uptake of soluble antigen into afferent ileal lymph following intra-intestinal infusion of soluble or particulate antigen.

Experiments were carried out in sheep to determine the isotype distribution of antibody-containing cells (ACC) produced by the lamina propria of the intestine. Soluble or particulate antigen was infused intra-intestinally and the isotype specificity of the subsequent ACC response was monitored in afferent lymph collected from ileal lymphadenectomised sheep. Infusion with Brucella abortus cells+5% DEAE-dextran for 3 days elicited a peak lymph-borne ACC response of 5 X 10(5) ACC/hr on day 7, and a second 3-day infusion elicited a somewhat reduced response with a peak output of ACC of 2.9 X 10(5)/hr on day 12. Brucella-specific ACC were of either IgM or IgA isotype, and a percentage of cells apparently contained both isotypes during the primary response. Following continuous intra-intestinal infusion of ovalbumin with DEAE-dextran, peak levels of ACC in lymph occurred on day 9 when 10.7 X 10(5)/hr ACC were present in lymph, and on day 15 when 16.5 X 10(5) ACC/hr were discharged into lymph. IgA-ACC comprised 70-90% of ACC throughout the response, with 5-25% IgM-ACC produced in the early stages. IgG1-ACC assumed a greater proportion of the total ACC as the response progressed. A solid-phase radioimmunoassay was used to measure the long-term absorption of ovalbumin from the ileum. The cumulative uptake was similar, whether ovalbumin was infused with or without DEAE-dextran, although following infusion with DEAE-dextran, measurable amounts of ovalbumin were present in lymph for a longer period. These results confirm that the intestinal epithelium is permeable to minute amounts of macromolecules, and the prolonged permeability may contribute to the immunopotentiating effect of DEAE-dextran.