Variables affecting the local immune response in Thiry-Vella loops. II. Stability of antigen-specific IgG and secretory IgA in acute and chronic Thiry-Vella loops.

Abstract The predominant mucosal immune response to antigens administered into Thiry-Vella loops in rabbits has been IgA with little or no antigen-specific IgG detected in the intestinal secretions. However, there has been no evidence that antigen-specific IgG could be recovered at all if IgG were being secreted in response to the locally administered antigen. In the present study, solutions containing either IgG or IgA activity against a Shigella flexneri-Escherichia coli hybrid (shigella X16) were incubated in vivo in Thiry-Vella loops of 10 rabbits and in vitro at 37 °C in pooled freshly collected intestinal secretions. The volume of fluid recovered from chronic Thiry-Vella loops was significantly decreased after 10 min or longer of in vivo incubation. After 100 min of in vivo incubation an average of 50% of the antigen-specific IgA activity and 42% of the antigen-specific IgG activity could be recovered. Complete recovery of both the IgA and IgG activity was achieved in the in vitro incubations. Gel diffusion studies demonstrated that the IgA and IgG activity remaining after 100 or 200 min of in vivo incubation was in the m.w. range of intact dimeric secretory IgA and intact monomelic IgG, respectively. These studies indicate that the stability of both IgG and secretory IgA in the lumen of Thiry-Vella loops is sufficient to allow their detection by sensitive immunochemical techniques.