Increased disease burden in Interleukin-3 deficient mice after Mycobacterium tuberculosis and herpes simplex virus infections

Interleukin-3 (IL-3) is produced during infections caused by parasites, bacteria and viruses, but its contribution to immunity in this context remains largely unknown. In mouse models of parasitic infections, in which the effects of IL-3 have been most extensively studied, IL-3 has been variously reported as protective, detrimental or inconsequential. Similarly, mixed results have been reported in viral and bacterial infection models. Here, we investigated the effects of IL-3 in mouse models of Mycobacterium tuberculosis and herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) infections by assessing the pathogen burden, disease manifestations and survival following infection. After infection with M. tuberculosis, IL-3 deficient mice showed higher bacillary burden, increased lung pathology and reduced survival compared to wild type mice. After infection with HSV-1 through cutaneous route and HSV-2 through vaginal route, IL-3 deficient mice showed higher viral burden, increased disease manifestations and reduced survival compared to wild type mice. Our results show that IL-3 makes a subtle but significant contribution to protective immunity in these mouse models of bacterial and viral infections.