Psoriatic arthritis joint fluids are characterized by CD8 and CD4 T cell clonal expansions that appear antigen driven

The CD8 alpha betaT cell receptor repertoire In joint fluid of individuals with active psoriatic arthritis contained an average of 32 major oligoclona l expansions in many variable genes of the TCR beta chain (BV) families, as shown by beta chain CDR3 length analysis. Interestingly; a small number of oligoclonal expansions mere shared between simultaneous samples of joint f luid and blood; however, most expansions found in joint fluid were not iden tifiable in blood emphasizing the immunologic specificity of the clonal eve nts for the inflamed joint at a given point of time. The CD4 T cell joint f luid repertoire contained fewer and smaller oligoclonal expansions also lar gely restricted to the joint, suggesting that CD4T cells participate perhap s by interacting cognitively to generate the CD8 clones. The inferred amino acid sequence of a single CD8 oligoclonal expansion revealed that they usu ally are composed of one or a few structurally related clones at the amino acid sequence level with beta -chains that encode identical or highly homol ogous CDR3 motifs, These were not shared among patients. Moreover, several clones that encoded the same amino acid sequence were found to be structura lly distinct at the nucleotide level, strongly implying clonal selection an d expansion is operating at the level of specific TCR-peptide interactions. The findings support a model of psoriatic arthritis inflammation involving extensive and selective Ag, likely autoantigen, driven intra-articular CD4 , and CD8 T cell clonal expansions.