SLAM family receptors are involved in humoral immune regulation. In this issue of JEM, Zhong et al. provide evidence that these receptors collectively suppress germinal center reaction but promote production of antigen-specific antibodies. SLAM family receptors are involved in humoral immune regulation. In this issue of JEM, Zhong et al. (2021. J. Exp. Med. https://doi.org/10.1084/jem.20200756) provide evidence that these receptors collectively suppress germinal center reaction but promote production of antigen-specific antibodies.