Prolactin enhances the in vitro production of IgG in peripheral blood mononuclear cells from patients with systemic lupus erythematosus but not from healthy controls

Objectives-Recent evidence suggests that prolactin (PRL) plays a part in th e pathogenesis of systemic lupus erythematosus (SLE). Because B cell hyperr eactivity and autoantibodies are characteristic hallmarks of SLE, this stud y aimed at assessing the impact of this pituitary hormone on IgG production by stimulating peripheral blood mononuclear cells (PBMC) with PRL. Methods-PBMC from 11 patients with SLE assessed by the ECLAM score and eigh t healthy controls were incubated with PRL and cultured for seven days. IgG production was measured by enzyme linked immunosorbent assay (ELISA). Results-Spontaneous IgG production of SLE PBMC was significantly enhanced c ompared with that found in healthy controls. After PRL stimulation, the IgG concentrations of supernatants from SLE PBMC were significantly higher tha n those of unstimulated PBMC (median 394 ng/ml). Of note, the physiological concentration of PRL (20 ng/ml) induced IgG production more effectively (m edian 1139 ng/ml) than PRL at 100 ng/ml (median 1029 ng/ml). In contrast, p reincubation with PRL did not stimulate IgG production in normal PBMC. A si gnificant correlation between PRL induced IgG production and the disease ac tivity (ECLAM) of the patients with SLE was seen. Moreover, the maximum amo unt of PRL induced IgG depended on the serum PRL concentrations of the pati ents with SLE. Conclusions-The results suggest that PBMC from patients with SLE have an ex traordinarily high susceptibility to PRL, showing the most striking effect at a concentration usually found in vivo. This indicates a potential role f or mild hyperprolactinaemia in the pathogenesis of SLE, influencing both Ig G production and disease activity.