Retinoic acid receptor β deficiency reduces splenic dendritic cell population in a conditional mouse line

Different studies have shown that retinoids and their receptors [retinoic acid receptors (RARs) and retinoid X receptors (RXRs)] have crucial effects on the differentiation and function of myeloid cells such as Dendritic cells (DCs) and the development of lymphoid tissue. However, the relationship between RARβ expression and DCs has not been previously studied in vivo. This work examined the effect of decreased RARβ expression on the number (and probably on differentiation) of splenic DCs and the structure of spleen using a conditional mouse that partially ablates floxed RARβ gene (RARβ(L-/L-) mice). Our results showed that RARβ is expressed mainly in cells of the splenic White Pulp (WP) zone of Wild type mice. As expected, low levels of RARβ expression were detected in the spleen of RARβ(L-/L-) conditional mice. These results were consistent with a decrease in the population of splenic CD11c(+)MHC-II(+) cells. Histopathological analyses of conditional mice spleen indicated defects in cell organization and structure. The expression of Toll-like receptor 2 was also down-regulated in the spleen of these mice. These results suggest that RARβ is involved in splenic cell organization as well as in the maintenance of splenic DCs population, indicating that RARβ expression is important in homeostasis of immune system components.