Prolactin Mediates Photoperiodic Immune Enhancement: Effects of Administration of Exogenous Prolactin on Circulating Concentrations, Receptor Expression, and Immune Function in Steers1

Abstract

Changes in photoperiod can significantly impact the physiology of many species. For example, we have observed an improvement in cellular immune function in cattle on short-day photoperiod (SDPP) relative to long-day photoperiod (LDPP). In addition, prolactin (PRL) and PRL receptor (PRL-R) are affected by photoperiod management. Our hypothesis is that the inverse relationship observed between PRL and PRL-R mRNA expression during photoperiod treatment alters the sensitivity of the animal to PRL, thereby affecting the changes in their cellular immune function. The objective of this study was to determine the effects of exogenous PRL on photoperiodic-mediated immune responses. Eight Holstein steers received each of four treatments: LDPP (16L:8D), SDPP (8L:D), SDom (SDPP plus PRL via osmotic minipump for 10 days), and SDinj (SDPP plus PRL via 3x daily injections for 10 days). Steers on SDPP had decreased PRL relative to the other treatments. Expression of PRL-R mRNA was increased in SDPP animals relative to LDPP, SDom, and SDinj. Prior to PRL treatment, SDPP animals had greater lymphocyte proliferation and neutrophil chemotaxis relative to LDPP animals. Following PRL treatment, cellular immune function of SDom and SDinj animals was reduced to the level of LDPP animals. Addition of PRL to the in vitro lymphocyte proliferation did not alter response of LDPP animals but increased proliferation of lymphocytes from SDPP animals. The results of these experiments suggest that an animal's responsiveness to PRL correlate to changes in cellular immune function that occur with photoperiod manipulation.

Evidence for a Role of Prolactin in Mediating Effects of Photoperiod during the Dry Period

“…The findings of this study are consistent with previous observations that PRL concentrations are increased in dry cows exposed to LDPP compared with SDPP cows [ 12 , 17 , 27 ]. In previous experiments, osmotic minipumps were used in steer calves to increase circulating PRL in SDPP treated animals to concentrations similar to LDPP animals, and a concomitant shift in immune function similar to calves on LDPP was observed in SDPP+PRL calves [ 28 ]. In part because the supply of recombinant bovine PRL was limited in the present study, PRL concentrations were increased in SDPP+PRL relative to SDPP cows, but lower than LDPP cows.…”

Whole genome gene expression changes and hematological effects of rikkunshito in patients with advanced non-small cell lung cancer receiving first line chemotherapy

“…CD19 and MS4A3 both serve important roles in B cell receptor (BCR) activation and signaling ( 44 , 45 ), while the extracellular antigen recognizing domain is complexed with CD79A and CD79B that form the cytoplasmic tail of the BCR ( 46 ). TNFRSF13B affects T-cell-independent antibody responses ( 47 ) and PRL may promote the increased proliferation of lymphocytes ( 48 ). In the present study, CD19 , MS4A3 , CD79A , CD79B , TNFRSF13B , TNFRSF17 and PRL were all up-regulated following rikkunshito treatment, indicating that it may enhance the activation and proliferation of B cells.…”

Neuroendocrine control of photoperiodic changes in immune function

“…Short-days typically induce reductions in circulating prolactin concentrations (Auchtung & Dahl, 2004; Goldman & Nelson, 1993). Prolactin is unique in that it is broadly immunoenhancing and consistently increased in long day conditions, and exogenous prolactin administration can promote a long day immune phenotype (Auchtung & Dahl, 2004).…”

“…Prolactin is unique in that it is broadly immunoenhancing and consistently increased in long day conditions, and exogenous prolactin administration can promote a long day immune phenotype (Auchtung & Dahl, 2004). …”