title: C3 promotes expansion of CD8+ and CD4+ T cells in a Listeria monocytogenes infection.
abstract: It is known that C3 is required for optimal expansion of T cells during acute viral infections. However, it is not yet determined whether T cell responses to intracellular bacterial infections require C3. Therefore, we have investigated the requirement for C3 to elicit potent T cell responses to Listeria monocytogenes (LM). We show that expansion of Ag-specific CD8 and CD4 T cells during a primary response to LM was markedly reduced in the absence of C3 activity. Further studies indicated that, unlike in an influenza virus infection, the regulation of LM-specific T cell responses by C3 might not involve the downstream effector C5a. Moreover, reduced T cell responses to LM was not linked to defective maturation of dendritic cells or developmental anomalies in the peripheral T cell compartment of C3-deficient mice. Experiments involving adoptive transfer of C3-deficient CD8 T cells into the C3-sufficient environment of wild-type mice showed that these T cells do not have intrinsic proliferative defects, and a paracrine source of C3 will suffice for clonal expansion of CD8 T cells in vivo. However, stimulation of purified C3-deficient CD8 T cells by plastic-immobilized anti-CD3 showed that C3 promotes T cell proliferation directly, independent of its effects on APC. On the basis of these findings, we propose that diminished T cell responses to LM in C3-deficient mice might be at least in part due to lack of direct effects of C3 on T cells. These studies have furthered our understanding of C3-mediated regulation of T cell immunity to intracellular pathogens.
authors: Department of Pathobiological Sciences, University of Wisconsin, Madison, WI 53706, USA.
authors: Yumi
authors: Y
authors: Nakayama
authors: Shin-Il
authors: SI
authors: Kim
authors: Eui Ho
authors: EH
authors: Kim
authors: John D
authors: JD
authors: Lambris
authors: Matyas
authors: M
authors: Sandor
authors: M
authors: M
authors: Suresh
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000382:microbiology*; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000382:microbiology*; D049109:Cell Proliferation; D003176:Complement C3 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D008089:Listeria monocytogenes / Q000276:immunology; D008088:Listeriosis / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D044087:Receptor, Anaphylatoxin C5a / Q000172:deficiency / Q000235:genetics / Q000502:physiology
chemical_list: D003176:Complement C3; D044087:Receptor, Anaphylatoxin C5a