The CD4+ T cell immunodominant Anaplasma marginale major surface protein 2 stimulates γδ T cell clones that express unique T cell receptors

Abstract

Major surface protein 2 (MSP2) of the bovine rickettsial pathogen Anaplasma marginale is an abundant, serologically immunodominant outer membrane protein. Immunodominance partially results from numerous CD4+ T cell epitopes in highly conserved amino and carboxy regions and the central hypervariable region of MSP2. However, in long-term cultures of lymphocytes stimulated with A. marginale, workshop cluster 1 (WC1)+ gammadelta T cells and CD4+ alphabeta T cells proliferated, leading to a predominance of gammadelta T cells. As gammadelta T cells proliferate in A. marginale-stimulated lymphocyte cultures, this study hypothesized that gammadelta T cells respond to the abundant, immunodominant MSP2. To test this hypothesis, gammadelta T cell clones were isolated from MSP2 vaccinates and assessed for antigen-specific proliferation and interferon-gamma secretion. Seven WC1+ gammadelta T cell clones responded to A. marginale and MSP2, and three of these proliferated to overlapping peptides from the conserved carboxy region. The gammadelta T cell response was not major histocompatibility complex-restricted, although it required antigen-presenting cells and was blocked by addition of antibody specific for the T cell receptor (TCR). Sequence analysis of TCR-gamma and -delta chains of peripheral blood lymphocytes identified two novel TCR-gamma chain constant (Cgamma) regions. It is important that all seven MSP2-specific gammadelta T cell clones used the same one of these novel Cgamma regions. The TCR complementarity-determining region 3 was less conserved than those of MSP2-specific CD4+ alphabeta T cell clones. Together, these data indicate that WC1+ gammadelta T cells recognize A. marginale MSP2 through the TCR and contribute to the immunodominant response to this protein.

Specific Recognition of Mycobacterial Protein and Peptide Antigens by γδ T Cell Subsets following Infection with VirulentMycobacterium bovis

“…Both WC1.1 + and WC1.2 + gd T cells respond to M. bovis WC1 has been hypothesized to act as a PRR on bovine gd T cells, binding pathogen components and lending specificity or amplification to TCR-mediated Ag recognition (21). In support of this, the serologically defined WC1.1 + gd T cell subpopulation responds specifically to Leptospira, and WC1 plays a direct role in this recall response (29,30), whereas the serologically defined WC1.2 + gd T cell subpopulation responds specifically to infection with A. marginale (48). Serologically defined WC1.1 + gd T cells selectively accumulate in the lungs and draining LNs of animals vaccinated with M. bovis BCG (34); however, it has not been clearly proven that WC1.1 + gd T cells are the dominant subset mediating the M. bovis-specific gd T cell response.…”

“…gd T cells respond to stimulation via their TCR, but they also can recognize microbial products through PRRs, such as WC1 and TLR (14,48,70,71). Thus, we next chose to determine whether gd T cell recognition of mycobacterial protein and peptide Ags requires signaling through the TCR.…”

“…Purified gd T cells were labeled with CFSE and cultured with or without IL-2 and the indicated Ags. gd T cells require contact with an APC to respond to Ag; however, because gd T cell Ag recognition is not MHC restricted, both autologous and allogeneic APCs are known to mediate gd T cell activation (48,59,60). We chose to include autologous peripheral blood monocytes in the cultures at a 1:5 ratio to purified gd T cells.…”

“…Purified gd T cells and monocytes were cultured with 10 U/ml recombinant human IL-2 (Sigma, Poole, U.K.). For TCRblocking experiments, purified gd T cells and monocytes were cultured for 1 h with 20 mg/ml anti-bovine gd TCR (GB21A) or mouse IgG2b isotype control (BD Biosciences, San Jose, CA) prior to the addition of Ag (48). For MHC class I-and MHC class II-blocking experiments, monocytes were cultured for 1 h in 20 mg/ml each anti-bovine MHC class I (H58A) (49), anti-bovine MHC class II (TH14B and TH22A) (50), or mouse IgG2a isotype control (BD Biosciences) prior to the addition of purified gd T cells.…”

Klinik Olarak Anaplasmosis Şüphesi Olan Ruminantlarda cELISA’nın Tanısal Değerinin Belirlenmesi

“…However statistical analyses revealed that seropositivity rates were not differ among age groups of sheep and goat. On the contrary; young cattle (0-12 months) showed also high infection rate, this may be due to maternal antibodies in the colostrum [24] . Our results cleared that Anaplasmosis is a disease of adults; a parallel findings were recorded by Chahan et al [25] and Keleş et al [26] .…”