Circulating levels of prolactin are elevated in patients with rheumatoid arthritis: a meta-analysis

Interference of B lymphocyte tolerance by prolactin in rheumatic autoimmune diseases

Systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and systemic sclerosis (SSc) are the most common rheumatic autoimmune diseases/disorders (RADs) that affect autologous connective tissues as a result of the breakdown of the self-tolerance mechanisms of the immune system. Prolactin, a glycoprotein hormone, has been known for its crucial role in the pathogenesis of these rheumatic autoimmune diseases. In addition to regulating lymphocyte proliferation and antibody synthesis, prolactin is also responsible for regulating cytokine production. Moreover, it contributes to the breakdown of central and peripheral tolerance mechanisms of B lymphocytes. Given the crucial role of prolactin in the pathogenesis of the mentioned RADs, prolactin may contribute to their pathogenesis by the breakdown of tolerance. In the present study, the key role of prolactin to the breakdown of B lymphocyte tolerance and its possible implication for the pathogenesis of these diseases is discussed. Current literature supports prolactin's role in the breakdown of B lymphocyte central and peripheral tolerance mechanisms, such apoptosis, receptor editing, and also anergy. Therefore, prolactin may contribute to the pathogenesis of RADs by the breakdown of B lymphocyte tolerance. However, more investigations, particularly in RA and SSc animal models, are required to precisely address the pathologic role of prolactin.

Prolactin peptide (pPRL) induces anti-prolactin antibodies, ROS and cortisol but suppresses specific immune responses in rainbow trout

Prolactin has several immune functions in fish however, the effects on innate and specific components of rainbow trout immunity are currently unknown. Therefore in this study, prolactin peptide (pPRL) injection in rainbow trout generated anti-PRL antibodies that were confirmed through Western blot assays of fish brain tissue extract. At the same time, this group of fish was immunized with a viral antigen (VP2) and the specific antibody titer generated by the rainbow trout was subsequently determined, as well as the sero-neutralizing capacity of the antibodies. Interestingly, this group of fish (pPRL-VP2) generated approximately 150% less antibodies compared with fish immunized only with the viral antigen (VP2), and pPRL-VP2 fish increased their cortisol level by 4 times compared to the control. Additionally, through qPCR assay, we determined that the pPRL-VP2 fish group decreased pro-inflammatory transcript expression, and the serum of these (pPRL-VP2) fish stimulated ROS production in untreated fish leukocytes, a phenomenon that was blocked by the pharmacological cortisol receptor inhibitor (RU486). Collectively, this is the first report that indicates that pPRL could modulate both components of immunity in rainbow trout.