sex-specific differences in a type of immune cell called regulatory T cells, or "Treg cells," and in the production of proteins called antibodies.
The "humeral response," the production of antibodies, is dysregulated in Covid-19. Treg cells were suspected to be responsible for this, as their role in the immune system is to regulate other immune cells and suppress their activities to control the strength of the immune response.
The T-follicular regulatory cells (Tfr cells), a subset of the Treg cell population are responsible for control of antibody production.
The study, published in the journal Proceedings of the National Academy of Sciences, observed that male patients lose circulating Tfr cells at a faster rate than female patients.