Paracoccidioides brasiliensis-stimulated human gamma/delta T cells support antibody production by B cells.

Paracoccidioidomycosis patients show hyperactive humoral immune responses. Consequently, we investigated whether cytokines in supernatants from Paracoccidioides brasiliensis-stimulated gamma/delta T cells support B-cell activation. We detected proliferation of B cells and increased immunoglobulin M (IgM) and IgG production. Thus, gamma/delta T cells may participate in polyclonal B-cell activation during paracoccidioidomycosis.

Human cord blood T-cell receptor alpha beta cell responses to protein antigens of Paracoccidioides brasiliensis yeast forms.

Paracoccidioides brasiliensis causes a chronic granulomatous mycosis, prevalent in South America, and cell-mediated immunity represents the principal mode of protection against this fungal infection. We investigated the response of naive cord blood T cells to P. brasiliensis lysates. Our results show: (1) P. brasiliensis stimulates T-cell expansion, interleukin-2 (IL-2) production and differentiation into cytotoxic T cells; (2) T-cell stimulation depends on P. brasiliensis processing and major histocompatibility complex (MHC) class II expression; (3) the responsive T-cell population expresses alpha beta T-cell receptors (TCR) with different V beta gene products, CD4 and CD45RO; (4) the P. brasiliensis components involved in T-cell expansion primarily reside in a high molecular weight (100,000 MW) and a low molecular weight (< 1000 MW) protein fraction. These results indicate that protein antigens of P. brasiliensis stimulate cord blood CD4 alpha beta T cells, independent from in vivo presensitization, and thus question direct correlation of positive in vitro responses with protective immunity in vivo.

Human alpha beta and gamma delta T cells from unexposed individuals respond to protein antigens of the yeast form of Paracoccidioides brasiliensis.

Paracoccidioides brasiliensis, a dimorphic fungus, causes chronic granulomatous mycosis in susceptible individuals. Different reports have shown that cell-mediated immunity is essential for protection against systemic mycosis, including paracoccidioidomycosis. We analyzed the reactivity of alpha beta and gamma delta T cells from unexposed Caucasian donors to P. brasiliensis yeast form components. Our results indicate: (i) alpha beta and gamma delta T cells proliferate after in vitro stimulation with lysates of P. brasiliensis; (ii) similar numbers of alpha beta T cells (f = 1/21,000) and of gamma delta T cells (f = 1/8000) respond to P. brasiliensis; (iii) P. brasiliensis-reactive gamma delta T cells express the V gamma 9V delta 2 TCR; (iv) the stimulatory activity of P. brasiliensis for both alpha beta and gamma delta T cells primarily resides in a high molecular weight (100 kDa) and in a low molecular weight (< 1 kDa) fraction; (v) the ligands responsible for stimulation of both alpha beta and gamma delta T cells are sensitive to proteinase treatment. We conclude that both alpha beta and gamma delta T cells from healthy individuals respond to ubiquitous protein antigens of P. brasiliensis.

Immunity to intracellular bacteria.

Immunity to intracellular bacteria including Mycobacterium tuberculosis, Mycobacterium leprae, and Listeria monocytogenes depends on specific T cells. Evidence to be described suggests that CD4 alpha/beta T cells, CD8 alpha/beta T cells and gamma/delta T cells which interact with each other and with macrophages contribute to acquired resistance against as well as pathogenesis of intracellular bacterial infections.