FUNCTIONAL ANATOMY OF THE LYMPHOCYTE IN IMMUNOLOGICAL REACTIONS IN VITRO

TLDR

In vitro, motile lymphocytes possess a prominent tail that attaches to other cells and debris, and these observations may have relevance to lymphocyte function in vivo. The authors propose the term “uropod” to designate a specialized cytoplasmic projection distinct from pseudopods. The uropod is anatomically and functionally distinct, serving as a unique attachment structure. Observations show that the uropod forms immediately after mitosis at the final cytoplasmic bridge between daughter cells, mediates interactions with macrophages, debris, and lymphoblasts during mixed leukocyte reactions, and suggests that immunologically committed cells can be recruited through both horizontal lymphoblast–lymphocyte interactions and vertical mitotic division.

Abstract

The motile lymphocyte in vitro has a prominent "tail" that becomes a means of "attachment" to other cells and debris during interaction. The term "uropod" is proposed to designate this specialized cytoplasmic projection which appears totally different, anatomically and functionally, from the pseudopods. Observations of lymphoblasts during mitosis indicate that the uropod is formed immediately following mitosis at the point of final cytoplasmic connection between daughter cells, a fact that may prove significant as lymphocyte function is better understood. In the mixed leukocyte reaction the lymphocyte interacts with macrophages, cell debris, and lymphoblasts via the uropod, suggesting that stimulatory material may be acquired through this specialized appendage. Lymphoblast-lymphocyte interaction is noteworthy and implies that immunologically committed cells may be mustered through horizontal as well as vertical processes: horizontally by lymphoblast-lymphocyte interaction and vertically by mitosis of transformed lymphoblasts. The possible relevance of these in vitro observations to lymphocyte functions in vivo is discussed.