There is overwhelming evidence that a single polypeptide serves as a receptor for both the Epstein-Barr Virus (EBV), and for certain enzymatic fragments of C3. This receptor, termed CR2 (CD21), is bnown to be expressed on the surfaces of B cells, and a large body of evidence suggests that CR2, or related structures, are also expressed on cells of the T hneage. Here, Constantine Tsoukas and John Lambris review the studies of CR2 expression in T cells and offer some speculation on its possible biological significance.

As far back as eighteen years ago, Shevach et al. described the cells from a patient with chronic leukemia that expressed both T-cell markers and C3 receptors. This observation was confirmed by Lin and Hsu-'and by Tnben and Smith 3, who described additional cases of T-cell leukemias that displayed C3 receptors. In addition, West and Herberman 4 demonstrated that Molt-4, an established T-lymphocytic leukemia line, also bore C3 receptors. The phenomenon is not, estricted to leukemic T cells: normal immature thymocytes also express C3 receptors 5, 6. These early studies, although intriguing, did not clearly delineate the precise nature of the C3 receptors