Summary M proteins, the major virulence factor of group A streptococci, have been implicated in the pathogenesis ofacute rheumatic fever (ARF) and other streptococcal related autoimmune diseases . A 22-kD fragment of M type 5 protein is a potent stimulant of human T cells and has recently been shown by our laboratory to belong to the newly designated family of superantigens . Using flow cytometry and the polymerase chain reaction, we demonstrate that this molecule reacts with subsets of human T cells expressing specific T cell receptor (TCR) VO elements, namely V,(32, 4, and 8. We employed similar techniques to analyze the TCR Va usage ofpep M5-stimulated T cells. These studies revealed that the preferential usage of particular Va elements is not specific for the superantigen; rather, it may reflect the repertoire of the individual being tested .
We have examined membrane protein profiles for alterations during red blood cell aging. To obtain populations of in vivoaged red cells, we maintained mice in a state ofcontinuous erythropoietic suppression for up to 8 wk using serial hypertransfusion. The circulating tl/2 of red cells from mice which had been erythropoietically suppressed for 8 wk was < 1 d compared with a t1/2 of 15 d for red cells from normal animals. The most obvious alteration in membrane proteins was an increase in the ratio of the membrane skeletal components 4.1a:4.1b from 0.3 for the normal red cell population to > 1 for these old cells. The 4.1a:4.lb ratio thus appears to be a useful index of red cell age. Analyses of the density profile of cells aged in the hypertransfused mice disclosed that these old cells had a density range similar to that of controls, suggesting that cell density does not increase significantly with red cell age in the mouse.
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