Follicle‐stimulating hormone receptor expression on leukocytes

Previous studies have shown that FSH induced a 7‐fold increase in IL‐1β secretion by peripheral blood mononuclear cells (PBMCs) isolated from young women during the follicular phase of their menstrual cycles (Corwin & Cannon, J Gender‐Specific Med 2:30–34, 1999). In addition, spontaneous in vitro shedding of soluble IL‐6α receptors and TNF type I receptors by PBMCs from postmenopausal women was inversely related to their plasma FSH concentrations (Brooks‐Asplund et al., Cytokine 19:193–200, 2002). These results suggest that the cells express receptors for FSH. To test this hypothesis, PBMCs were isolated by density gradient centrifugation, incubated with rabbit anti‐human FSH receptor, followed by a fluorescein‐conjugated goat anti‐rabbit IgG, then analyzed by flow cytometry. The monocytes and lymphocytes were discriminated by gating on the forward‐ and side‐scatter characteristics of the cells. Eight percent of the lymphocytes and 17% of the monocytes exhibited specific binding of the anti‐FSH receptor. In addition, PBMCs were lysed in Laemmli buffer, subjected to SDS‐PAGE electrophoresis on a 10% Tris‐HCl gel and electrophoretically transferred to a polyvinylidene difluoride membrane. The membrane was incubated with goat anti‐FSH receptor, followed by donkey anti‐goat IgG conjugated to HRP, and then color developed. The immunoreactive material extracted from human PBMCs was ~75 kDa and migrated parallel to purified FSH receptor from rat ovarian tissue. These results, obtained using two different primary antibodies against the FSH receptor, support the concept that human mononuclear cell reactivity to FSH is a receptor‐mediated process.