B-1 cells, a subtype of B lymphocytes, are found in lymphoid tissues and peritoneal and pleural cavities. They play diverse roles, releasing cytokines, generating antibodies, regulating the immune response, engaging in phagocytosis, and moving to inflammatory sites. However, their physiology remains partially understood, especially in stressful conditions like sleep restriction. This study aimed to investigate murine B-1 cell activation and differentiation under sleep restriction. Male C57BL/6J mice underwent an 18-hour sleep restriction for 21 days, followed by Candida albicans or Paracoccidioides brasiliensis infection. Purified peritoneal B-1 cells were evaluated for activation markers, microbicidal molecules, cytokine gene expression, Toll-like receptors, and commitment factors. Results showed that sleep restriction minimally influenced activation marker expression in B-1 cells across infection models. However, under sleep restriction, microbicidal molecule production increased in P. brasiliensis (NO) and C. albicans (ROS) infections. Gene expression revealed elevated TLR-2 and cytokines (IL-12, IL-6, TNF-α) in sleep-restricted animals. Lineage commitment analysis indicated myeloid polarization in sleep-restricted B-1 cells for all infection models. These findings underscore the impact of sleep restriction on B-1 cell activation and differentiation, with outcomes varying based on infection type. This study highlights the importance of investigating immunological changes resulting from sleep restriction.

Heat shock proteins (Hsps) are highly conserved molecules that are constitutively expressed and upregulated in response to physiological stress conditions. These immunogenic chaperones can have essential functions in fungi, particularly in dimorphic pathogens. Histoplasma capsulatum and Paracoccidioides species are dimorphic fungi that are the causative agents of histoplasmosis and paracoccidioidomycosis, respectively, which are systemic mycoses with significant rates of morbidity and mortality. Current treatment consists of long-term antifungal agents, and there is an urgent need for new therapeutic approaches with higher efficacy, lower toxicity, better biodistribution and improved selectivity. We engineered an immunoglobulin G1 (IgG1) isotype chimeric mouse-human monoclonal antibody, titled ch-MAb 4E12, from the parental IgG2a MAb 4E12, a monoclonal antibody to H. capsulatum Hsp60 that is protective in experimental histoplasmosis and paracoccidioidomycosis models elicited by H. capsulatum var. capsulatum and Paracoccidioides lutzii, respectively. The ch-MAb 4E12 increased phagolysosomal fusion and enhanced the yeasts uptake by PMA differentiated human THP1 macrophage cells in vitro. At low concentrations, the chimeric antibody significantly reduced the pulmonary and splenic fungal burden compared to an irrelevant antibody or no treatment. These results are the first to show that a chimeric mouse-human antibody can modify infection caused by dimorphic fungi.