Mycobacterium tuberculosis H37Rv Strain Increases the Frequency of CD3+TCR+ Macrophages and Affects Their Phenotype, but Not Their Migration Ability

Abstract

In mycobacterial infections, the number of cells from two newly discovered subpopulations of CD3+ myeloid cells are increased at the infection site; one type expresses the T cell receptor (CD3+TCRαβ+) and the other does not (CD3+TCRαβ−). The role of Mycobacterium tuberculosis (Mtb) virulence in generating these subpopulations and the ability of these cells to migrate remains unclear. In this study, monocyte-derived macrophages (MDMs) infected in vitro with either a virulent (H37Rv) or an avirulent (H37Ra) Mtb strain were phenotypically characterized based on three MDM phenotypes (CD3−, CD3+TCRαβ+, and CD3+TCRαβ−); then, their migration ability upon Mtb infection was evaluated. We found no differences in the frequency of CD3+ MDMs at 24 h of infection with either Mtb strain. However, H37Rv infection increased the frequency of CD3+TCRαβ+ MDMs at a multiplicity of infection of 1 and altered the expression of CD1b, CD1c, and TNF on the surface of cells from both the CD3+ MDM subpopulations; it also modified the expression of CCR2, CXCR1, and CCR7, thus affecting CCL2 and IL-8 levels. Moreover, H37Rv infection decreased the migration ability of the CD3− MDMs, but not CD3+ MDMs. These results confirm that the CD3+ macrophage subpopulations express chemokine receptors that respond to chemoattractants, facilitating cell migration. Together, these data suggest that CD3+ MDMs are a functional subpopulation involved in the immune response against Mtb.

Diverse Cell Death Mechanisms Are Simultaneously Activated in Macrophages Infected by Virulent Mycobacterium tuberculosis

“…However, a high level of IL-1β also indicates a pro-inflammatory profile. Moreover, using this in vitro infection model, we recently reported an increase in the frequency of CD3+TCR+ macrophages [ 8 ], supporting the hypothesis that this model favors a pro-inflammatory profile.…”

“…The virulence of M. tb modulates diverse macrophage functions. Recent findings show that H37Rv infection increases the migration frequency of pro-inflammatory CD3+TCRαβ+ macrophages [ 8 ]. It is probable that mycobacterial virulence allows the arrival of specific macrophages subpopulations.…”

“…Peripheral blood mononuclear cells (PBMCs) were isolated from buffy coats of healthy donors attending the blood bank at the INER, using the standard LymphoprepTM (Accurate Chemical-Scientific, Westbury, NY, USA) gradient centrifugation. For the enrichment of monocytes, we used a method previously reported [ 8 ]. Briefly, PBMCs were cultured for 2 h in a Corning ® 100 mm TC-treated culture dish (Corning, New York, NY, USA), allowing them to adhere.…”

“…Infection assays were performed as we previously reported [ 8 ]. First, a bacteria suspension was prepared for macrophage infection, and an aliquot of bacteria was thawed and centrifuged at 6000× g for 5 min.…”

“…This has been observed both in granuloma from TB patients and in murine models of BCG infection [ 5 , 6 , 7 ]. It has recently been reported that although a short time (24 h) of infection with virulent M. tb is not enough to increase the frequency of CD3+ macrophages, it is sufficient to increase that of CD3+TCRαβ+ macrophages [ 8 ].…”