Antigenic Stimuli do not Influence Thymic B Lymphocytes: A Morphological and Functional Study in Germ-Free and Conventionally Reared Piglets

We have recently reported that thymic B lymphocytes (TBL) are the first B-cell subpopulation undergoing isotype switching to IgG and IgA during embryonic life. The aim of this study is to analyze the influence of antigenic stimulation on TBL location and activity using a germ-free (GF) newborn pig model, in which maternal antibodies and antigens do not affect B-cell development. Immunohistological analysis showed that TBL were disseminated mainly in the thymic medulla. There were no differences in the distribution of TBL, both in GF newborn piglets before and after colonization with Escherichia coli and in older conventionally reared (CONV) piglets. The number of immunoglobulin (Ig)-secreting cells measured by the ELISPOT method was not influenced by microflora and food antigens. IgM-positive cells secreting IgM and CD45RC-positive cells spontaneously producing IgM, IgG, and IgA were detected in newborn thymus

Colonization of the intestine with nonpathogenic E. coli atrer birth reduces frewuency of allergies and tepeated infections later in life (after 10 and 20 years)

In our previous studies, the presence of an orally administered probiotic E.coli strain in the intestine stimulated a serum and local antibidy response