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Developmental Immunology
Volume 6, Issue 3-4, Pages 171-178
http://dx.doi.org/10.1155/1998/57820

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

1Department of Immunology and Gnotobiology, Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídeňská 1083, Prague 4 142 20, Czech Republic
2Department of Clinical Veterinary Science, University of Bristol, Langford, BS18 7DY, UK
3lnstitute for Care of Mother and Child, Prague, Czech Republic

Received 12 August 1996; Revised 14 August 1996; Accepted 2 May 1997

Copyright © 1998 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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.

Our findings suggest that TBL differentiation and Ig switching to IgG and IgA-secreting cells is not influenced by external antigens and that the thymic microenviroment plays an important role in this process.