Immune receptor complexes at the plant cell surface

•Ligand-induced dimerization is a hallmark of immune receptor complex assembly.•Ligand-induced co-receptor recruitment requires negative regulation of complex assembly in the absence of ligand.•Plant-associated microbes employ several strategies to avoid immune recognition. Immunity to microbial infection is a common feature of metazoans and plants. Plants employ plasma membrane and cytoplasmic receptor systems for sensing microbe-derived or host-derived patterns and effectors and to trigger inducible immune defenses. Different biochemical types of plasma membrane immune receptors mediate recognition predominantly of peptide and carbohydrate patterns. Current research highlights the role of immune receptor complex formation in plant immunity. In particular, ligand binding by immune receptors generates molecular surfaces that enable either receptor homo-dimerization or co-receptor recruitment for subsequent signal transduction. New insight into negative regulatory principles of immune receptor function further suggests substantial dynamics in protein–protein interactions at the plasma membrane that we are only beginning to understand.