Ia antigen expression by reticulum cells in lymphoid tissues and mesenchymal cells in the interstitium of the heart and liver of adult rats

Abstract

In an earlier series of studies on cellular labeling with [14C]adenine ([14C]A) in adult rats. Osogoe and his colleagues demonstrated the occurrence of certain cell types which are capable of incorporating [14C]A to a particularly great extent, such as the immature forms of either macrophage or fibroblast or reticulum cell lines. Further investigations have revealed that, among such cell types, a few fibroblastoid cells in the interstitium of the kidney and lung, as well as the proliferative reticulum cells in the intestinal lamina propria, express Ia antigen. In the present study, the reticulum cells in the lymphoid tissues and an appreciable number of mesenchymal cells in the interstitium of the heart and liver were also found to express Ia antigen. These two types of Ia-positive cells were characterized by a large cell body having a large euchromatic nucleus and abundant cytoplasm with dendritic processes. However, the mesenchymal cells were found in the interstitial tissue space of the organs, mostly scattered singly or occasionally grouped in small cell aggregations, without coexisting lymphoid cells. The biological significance of the Ia antigen expression by the two cell types, in particular the mesenchymal cells, is discussed in relation to their capacity for uptake of [14C]A.