Stimulation of rat B‐lymphocyte proliferation by corticotropin‐releasing factor

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Abstract
The mitogenic effect of corticotropin-releasing factor (CRF) on rat lymphocytes was investigated. When rat splenocytes were cultured for 48 hr with CFR, a dose-dependent increase in incorporation of 3H-thymidine (3H-Tdr) was observed, with a maximal response at 10 nM CRF. Comparison of the proliferative effect of CRF on enriched populations of B lymphocytes, T lymphocytes, or macrophages revealed that only B lymphocytes responded following treatment with CRF. When lymphocytes derived from different lymphoid tissues were compared, CRF had a greater proliferative effect on lymphocytes derived from gut-associated lymphoid tissue (mesenteric lymph nodes and Peyer's patches) than on lymphocytes from spleen or inguinal lymph nodes; CRF had no effect on thymocytes. Synthetic fragments of CRF were used to determine which portions of the peptide are recognized by lymphocytes. The C-terminal fragments α-helical CRF9–41 and CRF21–41 were as potent as native CRF in stimulating B-lymphocyte proliferation, whereas CRF1–20 did not stimulate proliferation. The activity of these peptides suggests that CRF stimulates lymphocyte proliferation by cellular recognition of structural determinants in the C-terminal one-half of the peptide.