AbstractGenetic background and T-cell expansion have been confirmed as the most important factors leading to psoriasis susceptibility in the Caucasian population. This study was performed to identify the T-cell receptor Vβ repertoire and HLA-Cw genotype in twenty Mexicans of two different ethnicities with severe chronic plaque-type psoriasis. HLA-Cw typing was performed to detect the allele pattern by SSP-PCR. In parallel, RT-PCR and Western blot were used for the identification of the TCR Vβ expression in peripheral blood cells. We identified a variety of HLA-Cw alleles in this group of patients distinct from the widely known HLA-Cw 0602 Caucasian allele. Moreover, TCR Vβ-2 and Vβ-7 clone-type frequencies were different and statistically significant (P = 0.0280). We speculate that because of diverse genetic backgrounds, the susceptibility to disease and activation of T-cells for a proper immune response could be specific; therefore, the findings might contribute to the elucidation of the pathogenesis in psoriatic Mexican patients.

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Bovine mastitis is a multifactorial disease that produces important losses in livestock and dairy industry. One of the main factors that causes this disease are microorganisms such as Staphylococcus aureus, which has multi-resistance to antibiotics and virulence factors such as its ability to internalize into bovine Mammary Epithelial Cells (bMECs), which allows bacteria to evade the host's immune system and persist inside the cell. However, Coagulase-Negative Staphylococci (CNS) have a significant role as bovine mastitis pathogens. S. agnetis is an emergent CNS pathogen isolated from bovine mastitis, whose capacity to internalize into bMECs is unknown. In the present work we characterized an isolate of S. agnetis from bovine mastitis, which was resistant to penicillin, dicloxacillin and ampicillin; also, the isolate showed resistance to methicillin through a mechanism that may be related to the presence of the mecA gene. In addition, S. agnetis internalized into bMECs (10% relative to S. aureus (ATCC 27543), which could be related to the presence of the fnbpA, clfB and spa genes. This is the first study that demonstrates the ability of internalization of S. agnetis into bMECs, which is a virulence factor that may represent a major problem in the management of bovine mastitis.