Association of elevated CD151+ T cell frequencies with impaired immune function

We recently reported that in humans the tetraspanin CD151 marks phenotypically distinct T cell subsets. The frequency of CD151+ T cells differs between T cell lineages and in between memory T cell populations. CD151+ T cells are hyper-proliferative and hyper-activated, as shown by phospho-proteomic analysis. We found that CD151 is an activation marker that is upregulated following TCR/CD3 activation, but at baseline, the presence of CD151 was associated with the loss of CD28 expression, a sign of T cell senescence. We hypothesized that the presence of CD151+ T cells is associated with immune hyperactivation and in extension, impaired immune surveillance. Unfortunately, we found that not even basic human CD151 T cell biology is reproduced in mouse models and thus had to resort to the study of pathological human conditions to elucidate the role(s) of CD151+ T cells. As cancer development requires immune escape, cancer diagnosis could be used as an indicator of impaired immune surveillance. Benefitting from the availability of longitudinal patient sample and data collections from people living with HIV (PLWH) we found that PLWH that developed cancer all had CD8+CD151+ T cell frequencies outside a normal reference range. CD8+CD151+ T cell frequency increase was not cancer-specific and could be detected years before the cancer diagnosis (0.5–12 years), indicating that the increase was not part of an anti-tumor response. Other established immune markers showed no correlation with the development of cancer. The findings associate elevated CD8+CD151+ T cell frequencies with impaired immune surveillance and suggest that elevated CD8+CD151+ T cell frequencies, at least in PLWH can be used as prognostic marker for cancer development. Supported by grants from NIH R01-AI122842, NIH R33-AI116188, NIH R33-AI133679