All Posts Tagged With: "T cells"

Excerpt:

The ability of the thymus to generate a population of T cells that is, for the most part, self-restricted and self-tolerant depends to a great extent on the Ags encountered during differentiation. We recently showed that mycobacteria disseminate to the thymus, which raised the questions of how mycobacteria within the thymus influence T cell differentiation and whether such an effect impacts host-pathogen interactions. Athymic nude mice were reconstituted with thymic grafts from Mycobacterium avium-infected or control noninfected donors. T cells generated from thymi of infected donors seemed generally normal, because they retained the ability to reconstitute the periphery and to respond to unspecific stimuli in vitro as well as to antigenic stimulation with third-party Ags, such as OVA, upon in vivo immunization. However, these cells were unable to mount a protective immune response against a challenge with M. avium. The observation that thymic infection interferes with T cell differentiation, generating T cells that are tolerant to pathogen-specific Ags, is of relevance to understand the immune response during chronic persistent infections. In addition, it has potential implications for the repertoire of T cells generated in patients with a mycobacterial infection recovering from severe lymphopenia, such as patients coinfected with HIV and receiving antiretroviral therapy.

Infectious agents have been implicated in the etiopathogenesis of various
vasculitides via numerous and overlapping mechanisms including direct microbial
invasion of endothelial cells, immune complex mediated vessel wall damage and
stimulation of autoreactive B and/or T cells through molecular mimicry and
superantigens. While the causative role of hepatitis B virus in polyarteritis
nodosa and hepatitis C virus in mixed cryoglobulinemia is clearly established,
evidence for the association of other infectious agents with vasculitis,
including human immunodeficiency virus, parvovirus B19, cytomegalovirus,
varicella zoster virus, Staphylococcus aureus, rickettsiaceae, Treponema
pallidum and Borrelia burgdorferi, among numerous others, is accumulating. The
spectrum of association of infectious agents; bacteria, viruses and parasites,
with systemic vasculitides, will be reviewed herewith. Continued