Generation of B lymphocytes and immunoglobulin diversity in Bos taurus
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1
University of Helsinki, Faculty of Veterinary Medicine, Department of Veterinary Biosciences, Finland
We have characterized B lymphopoiesis, germline IGLV, IGKV and IGHV repertoires and the mechanisms of the generation of the primary immunoglobulin repertoire in cattle.
B lymphopoiesis is active in fetal bovine bone marrow and lymph nodes, proceeding through CD79alpha+IgM- pre-B cells expressing RAGs and surrogate light chain.
TdT is selectively expressed in fetal bone marrow B cells, indicating diversification of the recombining Ig genes by junctional mechanisms.
During the last trimester of fetal development the immature B cells populate the ileal Peyer’s patch, generating oligoclonal lymphoid follicles with extremely rapid B cell turnover. AID is strongly expressed in the follicles, associated with hypermutation of the IGHV genes before exposure to external antigens. AID is also expressed in the spleen, but the ileal Peyer’s patch is likely quantitatively more significant to the generation of the diversified B cell pool due to the higher proliferation rate.
B lymphopoiesis is practically absent in the adult, possibly due to changes inherent to the hematopoietic lineage. Thus, cattle rely on the peripheral B cell pool generated in fetal and early postnatal period for the rest of the life.
The germline repertoire of Ig gene segments is very limited in cattle. There are a maximum of 33 functional paralogous light chain V genes dominated by a single subgroup, and a maximum of 20 functional paralogous heavy chain V genes belonging to a single clan II subgroup. Thus, junctional diversity and hypermutation are essential in the generation of sufficient primary immunoglobulin repertoire.
Keywords:
B cells,
B lymphocytes,
B lymphopoiesis,
Immunoglobulins,
repertoire,
Ig gene repertoire,
IgH locus,
light chain,
heavy chain,
activation-induced cytidine deaminase (AID),
AICDA,
Terminal deoxynucleotidyl transferase,
TDT,
hypermutation,
Peyer’s patches,
Peyer's patch,
junctional diversity,
Ruminants,
Ruminant,
Cattle,
Veterinary,
veterinary immunology
Conference:
15th International Congress of Immunology (ICI), Milan, Italy, 22 Aug - 27 Aug, 2013.
Presentation Type:
Abstract
Topic:
Adaptive Immunity
Citation:
Liljavirta
J,
Ekman
A,
Niku
M,
Pessa-Morikawa
T and
Iivanainen
A
(2013). Generation of B lymphocytes and immunoglobulin diversity in Bos taurus.
Front. Immunol.
Conference Abstract:
15th International Congress of Immunology (ICI).
doi: 10.3389/conf.fimmu.2013.02.00855
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Received:
20 Jun 2013;
Published Online:
22 Aug 2013.
*
Correspondence:
Prof. Antti Iivanainen, University of Helsinki, Faculty of Veterinary Medicine, Department of Veterinary Biosciences, University of Helsinki, 00014, Finland, antti.iivanainen@helsinki.fi