Abstract: | T-cell receptor (TCR) ß-chain usage and expression of the CD3, CD4, and CD8
differentiation antigens were analyzed in 14 spontaneous AKR lymphomas. Lymphoma
cells massively infiltrated and/or proliferated in the organs analyzed (thymus, spleen,
and mesenteric lymph nodes), giving rise to a loss of organ structure. One lymphoma
occurred only in the thymus, and failed to express CD3, CD4, and CD8. All other
lymphomas expressed the CD3/TCR complex. With respect to CD4 and CD8
expression, the lymphomas were either double-negative (DN), double-positive (DP), or
single-positive (SP). The frequency of DP (CD4+8+) lymphomas was low compared to the
frequency of DP thymocytes in a normal AKR thymus. A substantial heterogeneity was
seen in the intensity of CD4 and CD8 expression among various lymphomas, which was
independent of the level of CD3 expression. Considering TCR V ß gene family usage, 2
out of 14 lymphomas expressed V ß6. Normally, V ß6+ thymocytes are deleted from the
thymocyte pool at the immature DP stage of T-cell development in AKR mice. These
data support the hypothesis that the lymphocytes in the immature DP stage of T-cell
development are susceptible to the induction of AKR lymphomagenesis. The presence
of V ß6+ lymphoma cells indicates that the lymphomagenesis is accompanied by a
defective clonal deletion of cells expressing a possible autoreactive TCR. |