B Cell Ligand Discrimination Through a Spreading and Contraction Response

TLDR

B cells recognize antigens via surface immunoglobulin receptors and are most effectively activated by membrane‑bound ligands. The study proposes that dynamic spreading is a key step in the immune response. The authors observed a two‑phase B‑cell response—spreading followed by contraction—that concentrates antigen into a central aggregate, with the extent of this process determining antigen accumulation and activation, and simulations suggest this mechanism underlies affinity discrimination.

Abstract

B cells recognize foreign antigens by virtue of cell surface immunoglobulin receptors and are most effectively activated by membrane-bound ligands. Here, we show that in the early stages of this process, B cells exhibit a two-phase response in which they first spread over the antigen-bearing membrane and then contract, thereby collecting bound antigen into a central aggregate. The extent of this response, which is both signaling- and actin-dependent, determines the quantity of antigen accumulated and hence the degree of B cell activation. Brownian dynamic simulations reproduce essential features of the antigen collection process and suggest a possible basis for affinity discrimination. We propose that dynamic spreading is an important step of the immune response.