Increased expression of the PD-1/PD-L1 regulatory axis in tissue leukocytes from experimental actinomycetoma by Nocardia brasiliensis in BALB/c mice.

Abstract

The development of experimental actinomycetoma in mice pioneered the study of infective mechanisms in nocardiosis. However, the understanding of lymphocyte activation in actinomycetoma remains incomplete. In this study, we used flow cytometry to evaluate the cellularity and expression of regulatory receptors on leukocytes from spleen and infected tissue in a mice model of experimental actinomycetoma induced by Nocardia brasiliensis. Our results indicate that neutrophils dominate cellularity in infected tissue, representing >90 % of infiltrated leukocytes. Among lymphocytes, the percentage of Th1 and Tc1 cells decreases in spleen and infected tissue during chronic infection. Likewise, both tissues had similar changes in leukocyte expression of Programmed Cell Death Protein 1 (PD-1), T-cell immunoglobulin and mucin-domain containing-3 (TIM-3), and Programmed death-ligand 1 (PD-L1), suggesting the delayed systemic involvement of an initially local disease.