An understanding of the immunological footprint of Mycobacterium tuberculosis (MTB) CD4 T cell recognition is still incomplete. Here we report that human Th1 cells specific for MTB are largely contained in a CXCR3⁺CCR6⁺ memory subset and highly focused on three broadly immunodominant antigenic islands, all related to bacterial secretion systems. Our results refute the notion that secreted antigens act as a decoy, since both secreted proteins and proteins comprising the secretion system itself are targeted by a fully functional T cell response. In addition, several novel T cell antigens were identified which can be of potential diagnostic use, or as vaccine antigens. These results underline the power of a truly unbiased, genome-wide, analysis of CD4 MTB recognition based on the combined use of epitope predictions, high throughput ELISPOT, and T cell libraries using PBMCs from individuals latently infected with MTB. Mycobacterium tuberculosis is one of the most life-threatening pathogens of all time, having infected one-third of the present human population. There is an urgent need for both novel vaccines and diagnostic strategies. Here, we were able to identify the targets most dominantly recognized by latently infected individual that successfully contain infection. These targets are contained in three broadly genomic antigenic islands, all related to bacterial secretion systems and composed by several distinct ORFs. Thus, our results suggest that vaccination with one or few defined antigens will fail to replicate the response associated with natural immunity. Our analysis also pinpoints that the Th1 cells dominating the response are associated with novel and well-defined phenotypic markers, suggesting that the response is molded by unique MTB associated factors. This study demonstrates further that the approach combining peptide binding predictions with modern high throughput techniques is generally applicable to the study of immunity to other complex pathogens. Together, our data provide a new angle in the worldwide fight against M. tuberculosis and could be used for diagnostic or vaccine developments.

Neutrophil extracellular traps containing citrullinated peptides promote inflammation in synovial fibroblasts.

Objective: Rheumatoid arthritis (RA) is thought to be a T cell–mediated disease, based on its strong association with HLA class II alleles, clinical responsiveness to T cell–directed therapies, and the presence of CD4+ T cells in rheumatoid joints. The presence of anti–citrullinated protein antibodies (ACPAs) in RA serum and the association of these antibodies with HLA–DR4 alleles implicate citrulline‐specific autoreactive T cells in the development and progression of RA. The goal of this study was to determine the characteristics and specificity of autoreactive T cell responses in RA.Methods: We developed a panel of HLA–DRB1*04:01 tetramers, selecting citrullinated peptides from synovial antigens and verifying their immunogenicity in DRB1*04:01‐transgenic mice. Seven tetramers were used to examine the ex vivo frequency and surface phenotype of citrulline‐specific (Cit‐specific) T cells in patients with RA and healthy subjects with DRB1*04:01 haplotypes, using a magnetic enrichment procedure.Results: Cit‐specific T cells were detectable in peripheral blood samples from both healthy subjects and RA patients. In comparison to healthy subjects, RA patients had significantly higher frequencies of Cit‐specific T cells, and a greater proportion of these cells displayed a Th1 memory phenotype. Among RA patients, the frequency of Cit‐specific T cells was highest within the first 5 years after diagnosis of RA and was decreased in patients taking biologic agents, irrespective of disease duration.Conclusion: These findings link the presence of ACPAs in RA with Th1 cells specific for citrullinated epitopes and provide tools for disease‐specific immunomonitoring of autoreactive T cells.