Collectively, these outcomes demonstratein vivothat ablation of the variable macrophage immune receptor in murine lung tuberculosis is associated with suppression of CCL2 and defective granulomas formation

Collectively, these outcomes demonstratein vivothat ablation of the variable macrophage immune receptor in murine lung tuberculosis is associated with suppression of CCL2 and defective granulomas formation. == Figure 8. of granulomas, highly organized structures characterized by the presence of macrophages, which are considered to rely solely on invariant immune receptors. On the other hand, the presence of variable immune receptors is required for granuloma formation but this process is not solely dependent on T cells. Furthermore, TNF is required for the maintenance of the mycobacterial granuloma structure in humans. We now find evidence for subpopulations of human and mouse macrophages that express variable T cell receptors (TCR). Engagement of the macrophage-TCR triggers CCL2 release and phagocytosis of baits directed to this receptor is enhanced. TCR bearing macrophages accumulate in human tuberculosis granulomas and anti-TNF treatment of macrophages results in downregulation of the TCR, which is associated with caspase 3 cleavage and suppression of TCR. Anti-TNF treatment reduces mycobacteria induced cluster formation of TCR Tedizolid (TR-701) positive macrophages, which is in line with reduced granuloma formation Tedizolid (TR-701) in rag1/(T cell rag1+/+) and TNF/(T cell TNF+/+) chimeric mice. Consequently, both chimeras show reduced CCL2 staining after mycobacterial infection. In summary, we have identified a recombinatorial immunoreceptor in monocytes/macrophages and demonstrate its implication in mycobacterial infection. == Introduction == Macrophages are key players in major chronic inflammatory diseases including tuberculosis, atherosclerosis and rheumatoid arthritis. Based on their myeloid origin and professional phagocytic activity they are traditionally regarded as a pillar of innate immunity[1]. Tuberculosis is an infectious disease that in 2008 afflicted more than nine million individuals worldwide and claimed the lives of an estimated 1.3 million patients[2]. The disease is caused by mycobacteria that are efficiently contained by macrophages in highly organized immune structures, the tuberculous granulomas. Tedizolid (TR-701) Ample evidence indicates that the generation and maintenance of tuberculous granulomas require TNF[3],[4]. Moreover, reactivation of the disease by therapeutic TNF blockade is associated with disruption of the granuloma architecture that ultimately leads to spreading of the mycobacteria into the surrounding tissue[5]. Within the tuberculous granuloma, cellular immunity to mycobacteria is thought to be solely under the direction of T cells which orchestrate the macrophage host response to the pathogen. However, selective T cell depletion and reconstitution experiments in murine models of tuberculosis point to the involvement of variable host defense mechanisms in the control of mycobacterial infection beyond T cells[6]-[8]. The recent demonstration by our laboratory and others that neutrophils and eosinophils express T cell receptors (TCR) Rabbit polyclonal to AMIGO1 which are generated by V(D)J recombination has provided evidence for the existence of variable immune receptors outside lymphocytes[9]-[11]. These findings and the possibility that variable immune defense mechanisms outside T cells are implicated in the development of the tuberculous granuloma raise the question as to whether macrophages possess a molecular machinery for variable host defense. Here, we report that subpopulations of monocytes and macrophages express a recombinatorial TCR which is TNF regulated and demonstrate a role of this novel immune receptor in the macrophage host response to mycobacteria and the formation of the tuberculous granuloma. == Results == == Subpopulations of monocytes in the circulation and macrophages express the TCR == To assess the possibility that monocytes, like granulocytes[9]-[11], express the TCR, we isolated human CD14+monocytes from healthy donors (n = 12). Expression of the TCR in peripheral blood monocytes was assessed in MACS-CD14+purified cells by immunocytochemistry using antibodies to TCR/TCR and Tedizolid (TR-701) MHC-II. Utilizing this approach, we consistently detected a 5% cell fraction that displayed bright TCR+expression in freshly isolated CD14+monocytes which showed co-expression of MHC-II (Figure 1A). Purity of isolated CD14+monocytes was routinely Tedizolid (TR-701) >99.5% as determined by flow cytometry (Figure S1A). We next characterized the TCR expressing monocyte subpopulation in PBMC by flow cytometry. Consistent with immunocytochemistry, CD14+cells from three normal subjects displayed positive staining for TCR in a 34% subfraction which did not exhibit staining for the T cell marker CD3 (Figure 1B,Figure S1B). We then determined expression of the CR in monocyte-derived macrophages from three healthy donors. For this, monocytes were differentiated into nave, IFN activated and IL-4 activated macrophages, respectively, on glass slides for a period of 6 days[12]and stained for TCR. To quantify the TCR+populations in adherent macrophages, laser scanning cytometry (LSC) was performed on the slides that were immunostained with Alexa 555-labeled secondary antibodies. LSC analysis demonstrated that a 5% subpopulation of nave macrophages exhibited high fluorescence indicative of TCR expression (Figure 1C,Figure S1C). In contrast, the fraction of TCR bearing macrophages was significantly higher in the IL-4 (9%) and IFN activated macrophages.