CD5 is a potential selecting ligand for B cell surface immunoglobulin framework region sequences.
In rabbits nearly all B lymphocytes express the glycoprotein CD5, in contrast to mice and humans, where only a small proportion of B cells express this molecule (Raman, C., and K.L. Knight. 1992. J. Immunol. 149:3858-3864). CD5+ B cells appear to develop early in ontogeny and be maintained throughout life by self-renewal. The function of CD5 on B cells is still unknown. We showed earlier that "positive" selection occurs during B lymphocyte development in the rabbit appendix. This selection favors B cell expressing surface immunoglobulins with VHa2 structures in the first and third framework regions (Pospisil, R., G.O. Young-Cooper, and R.G. Mage. 1995. Proc. Natl. Acad. Sci. USA. 92:6961-6965). Here we report that F(ab')2 fragments, especially those bearing VHa2 framework region determinants, specifically interact with the B cell-surface glycoprotein CD5. This interaction can be inhibited by anti-CD5 antibodies. Furthermore, immobilized F(ab')2 fragments selectively bind CD5 molecules in appendix cell lysates. Interactions of VH framework region structures with CD5 may affect maintenance and selective expansion of particular B cells and thus contribute to autostimulatory growth of autoimmune or transformed cells.
Pospisil
R
R
Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Fitts
M G
MG
Mage
R G
RG
D000818:Animals; D001065:Appendix / Q000166:cytology / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D018956:CD5 Antigens / Q000276:immunology*; D002846:Chromatography, Affinity; D015326:Gene Rearrangement, B-Lymphocyte, Heavy Chain; D007140:Immunoglobulin Fab Fragments / Q000276:immunology*; D007143:Immunoglobulin Heavy Chains / Q000276:immunology; D007135:Immunoglobulin Variable Region / Q000276:immunology; D008213:Lymphocyte Activation; D011817:Rabbits
D018956:CD5 Antigens; D007140:Immunoglobulin Fab Fragments; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region