The sexes show profound differences in responses to infection and the development of autoimmunity. Dimorphisms in immune responses are ubiquitous across taxa, from arthropods to vertebrates. Drosophila melanogaster shows strong sex dimorphisms in immune system responses at baseline, upon pathogenic challenge, and over aging. We have performed an exhaustive survey of peer-reviewed literature on Drosophila immunity, and present a database of publications indicating the sex(es) analyzed in each study. While we found a growing interest in the community in adult immunity and in reporting both sexes, the main body of work in this field uses only one sex, or does not stratify by sex. We synthesize evidence for sexually dimorphic responses to bacterial, viral, and fungal infections. Dimorphisms may be mediated by distinct immune compartments, and we review work on sex differences in behavioral, epithelial, cellular, and systemic (fat body-mediated) immunity. Emerging work on sexually dimorphic aging of immune tissues, immune senescence, and inflammation are examined. We consider evolutionary drivers for sex differences in immune investment, highlight the features of Drosophila biology that make it particularly amenable to studies of immune dimorphisms, and discuss areas for future exploration.

The global demographic is shifting towards an aged population (United Nations, 2019). Yet, it is our oldest members of society that are the most vulnerable to infectious disease, reflecting immune system ageing, or "immunosenescence" (Glynn and Moss, 2020;Chen et al., 2021). Immunosenescence has two defining features: heightened susceptibility to pathogens, and increased systemic, basal inflammation (Franceschi, 2000;Zerofsky et al., 2005; Benayoun et al., 2019), which is strongly linked to the development of age-related diseases such as neurodegeneration and cancer (Franceschi