Background: It has been reported that T-cell depletion by in vivo treatment with monoclonal antibodies results in polyclonal B-cell activation. However, its effects on B cells responding to Galalpha1,3Gal (Gal) epitopes remain unknown.
Methods: alpha1,3-Galactosyltransferase-deficient (GalT-/-) mice were treated with depleting anti-CD4 and CD8 monoclonal antibodies. The kinetics of anti-Gal natural antibodies (NAb) and total immunoglobulin levels in their sera were evaluated. The frequencies of anti-Gal NAb-producing cells were determined in the various tissues of GalT-/- mice by enzyme-linked immunospot assay.
Results: In vivo T-cell depletion led to significant increases in both anti-Gal IgM and total IgM levels in sera of GalT-/- mice, but did not influence either anti-Gal IgG or total IgG levels. An increased frequency of anti-Gal and total IgM-producing cells was observed in the spleens and bone marrow of T-cell-depleted GalT-/-mice but not in peritoneal cavity cells.
Conclusion: In vivo T-cell depletion facilitates anti-Gal IgM production, suggesting that T cells deliver inhibitory signals to B cells responding to Gal.