B-cell profile, B-cell activating factor concentration and IgG levels in human cutaneous and mucosal leishmaniasis.

AIMS: The aim of this study was to evaluate characteristics of B cells in human tegumentary leismaniasis (TL) analysing cutaneous leishmaniasis (CL), most prevalent form and mucosal leishmaniasis (ML), aggressive form characterized by the destruction of the oral-nasal-pharyngeal cavities. METHODS AND RESULTS: By flow cytometry analysis, we found decreased percentages of non-class-switched memory B cells in TL with the degree of the loss related to clinical severity. Using commercial ELISA, we reported high levels of B-cell activating factor (BAFF) and IgG preferentially in aggressive CL and markedly in ML together with decreased BAFF receptors in the latter. We also found lower levels of BAFF after clinical recovery suggesting a relation between BAFF and disease activity. Mucosal leishmaniasis history of therapeutic failure presented high levels of BAFF accompanied by detectable concentrations of IFN-γ and IL-6 (assayed by commercial ELISA and cytometric bead arrays respectively), cytokines involved in exaggerated inflammatory responses and tissue damage in TL. CONCLUSION: We demonstrate B-cell disturbances in TL with the degree of the alterations related to clinical severity. We suggest a relation between excess of BAFF and disease activity and point towards a possible implication of BAFF in the inflammatory phenomenon of ML.

Increases in IgA(+) B cells in Peyer's patches during milk-borne mouse mammary tumor virus infection are influenced by Toll-like receptor 4 and are completely dependent on the superantigen response.

Mouse mammary tumor virus (MMTV) is a milk-borne betaretrovirus that has developed strategies to exploit and subvert the host immune system. Although mammary glands are the final target of infection, Peyer's patches (PP) are the entry site of the virus. Herein, we show that the infection induces increases in the number of PP IgA(+) B cells and higher expression of the α circular transcript, which is a specific marker of the switch to IgA. In addition, IgA(+) B-cell increases correlated with higher levels of cytokines related to IgA class switching, such as interleukin (IL)-5 and IL-6. Of interest, the increases in IgA(+) B cells were lower in Toll-like receptor 4-deficient mice and were completely dependent on the presence of superantigen-reactive T cells. Our results point to a novel mechanism involved in MMTV infection and suggest that IgA(+) B cells may play an important role in carrying the virus to the mammary glands.