CD4+ T Lymphocytes with Constitutive CD40 Ligand in Preautoimmune (NZB × NZW)F1 Lupus-Prone Mice: Phenotype and Possible Role in Autoreactivity

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Abstract
Lupus disease is marked by B lymphocyte hyperactivity and the production of Abs to dsDNA. The production of these anti-dsDNA Abs is T lymphocyte dependent. However, it is not clear how CD4+ T lymphocytes provide help for B lymphocytes to produce IgG anti-dsDNA Abs. One possible mechanism is suggested by studies showing that human patients with systemic lupus erythematosus and lupus mice have increased numbers of CD40 ligand (CD40L)+ T and B lymphocytes. The results described in this study reveal that young, clinically healthy lupus-prone New Zealand Black × New Zealand White F1 (BWF1) mice have naive CD4+ T cells with preformed CD40L. These cells contribute to a brisk response to immunization and to the production of anti-dsDNA Abs. In vitro experiments revealed that CD4+ T cells with preformed CD40L could, upon stimulation, provide antiapoptotic signals for B cells but could not induce proliferation or reduce activation threshold. These results suggest that the direct target cells for the effect of T cells with preformed CD40L in lupus may not be B lymphocytes.