Relationship between serum prolactin and mammary gland T-cell population in early lactating rats

MACKERN OBERTI, JUAN PABLO; NAVAS PAOLA B; PENNACCHIO GISELA E; VALDEZ SUSANA R; JAHN GRACIELA A

Buenos Aires, Argentina

Congreso; 1er Congreso Franco Argentino de Inmunología; 2010

Sociedad Argentina de Inmunología

@font-face { font-family: "Cambria"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; } Mammary stroma is composed of various cells, among them migratory leukocytes. Mammary lymphocytes are important during lactation, supplying maternal antibodies to milk. Recruitment of IgA secreting cells increases from parturition to late lactation. The role of T-cells recruited during pregnancy is unclear, but may be related to epithelial cell growth, protection against infections and immune response regulation. This homing pattern suggests that T cell recruitment is controlled by pregnancy- and lactation-specific stimuli. Our aim is to study the relationship between serum prolactin (PRL) levels and mammary T-cell populations in early lactation in order to increase the knowledge in hormone-induced lymphocyte homing. Female Sprague Dawley (SD) and OFA (SD derived desmoglein 4 -/- hairless phenotype with lactation deficit) rats were sacrificed at day 2 postpartum and trunk blood, mammary gland (MG) and corpora lutea (CL) were obtained to perform FACS, histological and RIA studies. Serum PRL was lower in OFA (16±3ng/ml n=12) than in SD rats (34±7ng/ml n=13; p<0,05). Mammary histology of OFA rats showed impaired development compared to SD (qualitative score, 1 to 5; SD, 4,6±0,4; OFA, 1,7±0,2; p< 0,05). FACS analysis showed lower percentage of MG CD3+ cells (from total leukocytes gating on CD45+ cells) in OFA (32±4%) compared to SD rats (43±4%; p<0,05), while CD11b+ cell levels were similar (SD, 21±1%; OFA, 19±1%). In CL the % of CD3+ cells were similar in SD and OFA rats (SD, 14±1%; OFA, 17±3%). OFA rats showed higher absolute and relative numbers of circulating CD3+ cells compared to SD (SD, 18±2% and 3121±811 cell/µl; OFA, 31±2% 5491±358 cell/µl; p<0,05), while CD11b+ cells were similar (SD, 43±4%; OFA, 41±3%).  These results show that MG T-cell population may be specifically affected in early lactating OFA rats and strongly suggest that serum PRL levels may be involved in mammary homing T-cell events, probably protecting the gland during lactation development.