IL1B and rheumatoid arthritis: While the general phenotype of M2 macrophages is retained, stimulation of these cells with IgG immune complexes and TLR ligands induces the selective induction of RA-associated cytokines TNFα, IL-1β, and IL-6, and promotes Th17 responses, in a spleen tyrosine kinase (Syk)-dependent way (14).