Rapidity and multiplicity of synthesis and expression of immunoglobulin isotypes by B lymphocytes in the small intestine.

An immunofluorescence double labeling assay was used to examine the kinetics of intestinal B lymphocytes with concurrent expression of multiple antibody isotypes in the mucosal tissues of rats infected with Trichinella spiralis (TS) muscle larvae for 1 to 15 days. As compared to the uninfected controls (day 0), the non-Peyer's patch tissues of the small intestine contained a significantly increased number of dual antibody-expressing B cells as early as 3 days after infection with a maximum proliferation of these B cells on days 7 and 10. These results indicate the rapidity of B cell response in the small intestine. Similar results were observed in the germinal centers of the Peyer's patches. The non-germinal centers of the Peyer's patch tissues showed delayed kinetics in B cell activation which occurred 10 days after infection. Quantification of the total number of B cells in these tissues was also carried out by staining the CD45RA marker on B cells with the OX33 monoclonal antibody. When comparing the total numbers of B cells with the numbers of B cells expressing dual isotypes of antibodies, our results showed the numbers of dual-expressing B cells (IgA:IgE, IgM:IgE, IgG1:IgE, IgG2a:IgE, IgG2b:IgE, and IgG2c:IgE), when combined, were over 7 times that of the total number of OX33-labeled B cells on day 7 in the small intestine. The dual-expressing B cells in the Peyer's patch-germinal center were more than 5 times that of the OX33-labeled B cells on day 15. These results therefore suggest that the dual-expressing B cells most likely synthesized and expressed more than two isotypes of antibodies during the peak days of the humoral response. Such phenomenon was not observed in non-germinal centers of the Peyer's patch tissues.