Not all plasma cells are made equal: well-hidden layers of heterogeneity.

Plasma cells (PCs) are the final stage of B cell development and sustain long-term humoral immunity by continuously secreting antibodies. Once considered a homogeneous population defined by a short-lived versus long-lived dichotomy, PCs are now recognised as highly heterogeneous. Recent advances have overturned several dogmas, revealing that long-lived plasma cells (LLPCs) can arise from diverse B cell precursors, and persist in tissues beyond the bone marrow. PC heterogeneity is shaped by intrinsic factors, including B cell origin, antigen affinity, BCR signalling strength and immunoglobulin isotype, as well as extrinsic factors such as tissue-specific microenvironments, cytokines and cellular interactions at induction and maintenance sites. Furthermore, temporal variables, termed "Moment", including age, sex, and inflammatory status, modulate PC fate throughout their maturation. This process also plays a central role in the emergence of heterogeneity within these LLPCs. Together, these parameters define a dynamic, context-dependent PC landscape with significant implications for immune regulation and vaccine design.