PROLACTIN, A LINK BETWEEN NEUROENDOCRINE AND IMMUNE-SYSTEM - ITS ROLEIN THE PATHOGENESIS OF RHEUMATIC DISEASES

Increasing evidence suggest that prolactin (PRL) has important immunor egulatory properties and may play a role in the pathogenesis and disea se expression of certain autoimmune diseases. Prolactin is co-mitogeni c on murine and human lymphocytes, induces the formation of IL-2 cell surface receptor and modulates the expression of various growth factor related genes. Prolactin also stimulates antibody production both in vivo and in vitro. Specific high affinity prolactin-receptors have bee n described on T and B lymphocytes as well as on monocytes. They are d istributed on heterogeneous lymphocyte subsets and they showed imbalan ce in autoimmune situations. Lymphocytes may produce PRL-like proteins biologically active that function as autocrine growth factors for lym phoproliferation. Hyperprolactinemia has been found in male patients w ith systemic lupus erythematosus (SLE) and also during pregnancy in SL E patients. Hyperprolactinemia is correlated with clinical and serolog ical activity in a subset of SLE patients. High levels of PRL aggravat es disease activity and accelerates mortality in the B/W mouse model o f SLE. In rheumatoid arthritis an excessive and upregulated secretion of PRL has been shown. Hyperprolactinemia has also been shown in a sub set of patients with primary Sjogren's syndrome. High PRL levels have been found in Reiter's syndrome patients and bromocriptine treatment h as been reported effective in these patients and psoriatic arthritis p atients. These data support a potential role of this immunoregulatory hormone in the pathogenesis of some rheumatic diseases.