Letter from the Editors —Volume 14 Issue 2, 2026

The immune system responds to signals from nearly every part of our physiology, including our microbiome, hormones, and reproductive organs. In this issue of IMMpress Magazine on Sex, Immunity and Reproduction, we explore what happens when we put these relationships at the centre of the conversation.

We begin with one of the most extraordinary examples of immune adaptation: pregnancy. Our infographic (p.8) introduces the shifting immunological landscape that accompanies gestation. From there, we explore two fascinating sites of immune regulation. ‘The Delicate Immunology of the Testes’ (p.10) examines testicular immune privilege and the mechanisms that allow reproductive cells to coexist with an immune system trained to recognize the unfamiliar. In ‘Undercover in the Uterus’ (p.12), we turn to maternal-fetal tolerance and the intricate immunological dialogue that allows a genetically distinct fetus to develop within the maternal environment. Reproductive biology has also inspired some unexpected chapters in medicine. We follow the scientific journey of Viagra (p.14), then explore immunocontraception (p.16), asking whether the immune system itself could be harnessed to develop new approaches to contraception, and the social questions that accompany those technologies.

Sex also shapes immunity far beyond reproduction. Women are disproportionately affected by many autoimmune diseases, and we examine the biology underlying this disparity (p.18). We then hear from Dr. Lena Serghides about her research at the intersection of infection, immunity, pregnancy, and placental biology (p.20). This issue also features pressing questions about infection and sexual health. We ask why an effective HIV vaccine remains so difficult to develop (p.22), while celebrating the success of the HPV vaccine and highlighting persistent global inequities in access (p.32).

Sex-based differences also appear in places such as bone health (p.23). Importantly, understanding these differences requires researchers to ask the right questions in the first place. We consider the consequences of historically excluding hormonal variation from experimental design and what can be lost when biological complexity is treated simply as noise (p.24).

Turning to our most intimate microbial ecosystems, we explore the vaginal and penile microbiomes and the case for approaching genital health at the level of couples rather than individuals (p.26). We also examine the inflammatory dimensions of endometriosis (p.28) and Polyendocrine Metabolic Ovarian Syndrome (PMOS) (p.29). We also make the case for an organ that might deserve considerably more attention from immunologists: the placenta, viewing it not merely as a conduit between parent and fetus, but as a dynamic immunological organ in its own right (p.30).

The relationships between hormones, sex, gender, and immunity also extend beyond reproductive physiology. We explore the impact of gender-affirming hormone replacement therapy on the immune system (p.34). Together, these stories remind us why studying sex in immunology requires both careful biological investigation and a willingness to rethink the assumptions that have historically shaped biomedical research.

Beyond our central theme, we also take a moment to celebrate our broader Canadian immunology community with our CSI 2026 Recap (p.36). Last but not least, we close the issue with our book review of Lousy Sex: Creating Self in an Infectious World (p.38). This book brings us back to many of the questions running through the pages of this issue: how reproduction, infection, immunity, evolution, and identity become entangled in ways that cannot be overlooked.

This issue is also particularly meaningful for another reason. For me, Manjula, it marks my final issue as Editor-in-Chief of IMMpress. Being part of this magazine and watching ideas move from conversations and rough drafts into the pages you are holding has been one of the most rewarding parts of my time in the Department of Immunology. I am incredibly grateful to every member of the IMMpress team I have had the opportunity to work alongside.

As always, none of this would be possible without our wonderful team of writers, senior editors, and designers, who volunteer their time and creativity to make each issue possible. Thank you for helping us bring this issue to life.

We hope you enjoy reading this issue as much as we enjoyed making it!

Editors-in-chief