What is the evidence (pro and con) that CD8+ T cells are important in the pathogenesis of PsA?
The association between PsA and class I MHC alleles provided preliminary evidence that CD8+ T cells may be of central importance in synovial inflammation. In this scheme, an antigen, presumably an infectious agent, triggers an aberrant CD8+ T cell response that mediates subsequent downstream inflammatory events. This model has been supported by studies indicating that psoriasis and PsA dramatically worsened in patients with acquired immune deficiency syndrome (AIDS) as the CD4+ cell counts dropped. Additional evidence came from studies of psoriatic synovial fluid showing a predominance of CD8+ T cells, some of which appear to have been generated by an antigen driven mechanism. CD4+ T cells are the predominant subset in psoriatic synovial membranes with ratios of CD4 to CD8 cells as high as 4:1. Secondly, recent studies from Zambia indicate that PsA improves with the onset of AIDS in human immunodeficiency virus (HIV) positive patients. Lastly, a dominant role for T cells in PsA has bee
