A Subset of Neutrophils Expressing Markers of Antigen-Presenting Cells in Human Visceral Leishmaniasis.

BACKGROUND: Visceral leishmaniasis (VL) is a potentially fatal parasitic disease associated with fever, cachexia and impaired protective T-cell responses against the parasite.

METHODS: Peripheral blood leukocytes from 105 subjects with VL and healthy control subjects from the endemic region of Muzaffarpur, Bihar, India, were compared using flow cytometry and reverse-transcriptase quantitative polymerase chain reaction. Findings were correlated with clinical data.

RESULTS: An expanded population of low-density neutrophils that expressed HLA-DR, CD80 and CD86 was observed in subjects with VL. This neutrophil population contracted after successful treatment of disease. Plasma from patients with acute VL was able to induce similar high-level HLA-DR expression in neutrophils from healthy subjects. HLA-DR+ neutrophils from subjects with VL did not stimulate T-cell proliferation, but they did express higher programmed cell death ligand-1 (PDL1) than other neutrophils, and lymphocytes of the same subjects expressed high programmed cell death 1 (PD1).

CONCLUSIONS: Patients with acute VL have expanded circulating low-density neutrophils expressing markers of antigen presentation, which diminish after treatment. Development of HLA-DR+ neutrophils is stimulated, at least in part, by components of plasma from patients with acute disease. Although we found no evidence that they act as antigen-presenting cells, these neutrophils expressed markers implicating a role in T-cell exhaustion.