Phenotypic and functional profiling of human proinflammatory type-1 and anti-inflammatory type-2 macrophages in response to microbial antigens and IFN-γ- and CD40L-mediated costimulation

Macrophages (Mphi) comprise a heterogeneous population of cells with various immune and homeostatic functions. Recently, we have described type-1 and type-2 human monocyte-derived Mphi subsets. Although both support outgrowth of intracellular mycobacteria, Mphi-1 secretes interleukin (IL)-23/IL-12 and supports T helper cell type 1 (Th1) responses, whereas Mphi-2 fails to produce IL-23/IL-12, predominantly secretes IL-10, and inhibits Th1 function. Here, we further describe the phenotypic and functional profiles of Mphi-1 and Mphi-2 in response to microbial antigens and interferon-gamma (IFN-gamma) and CD40L as costimulatory T cell back-talk signals. Activated IL-23(+)/IL-12(+) Mphi-1 secreted IL-1beta, IL-18, IL-6, and tumor necrosis factor-alpha (TNF-alpha), as well as IL-8, monocyte chemoattractant protein-1 (MCP-1), IFN-inducible protein 10 (IP-10), Mphi inflammatory protein-1beta (MIP-1beta), regulated on activation, normal T expressed and secreted (RANTES), Mphi-derived chemokine (MDC), and (low levels of) pulmonary and activation-regulated chemokine and thymus and activation-regulated chemokine (TARC), corroborating their proinflammatory function. Regardless of the stimulus, Mphi-2 maintained their IL-10(+) signature cytokine profile and produced no or relatively low levels of IL-12p40, IL-1beta, IL-6, TNF-alpha, MDC, or TARC. It is remarkable that Mphi-2 secreted high levels of IL-8, MCP-1, IP-10, MIP-1beta, and RANTES, suggesting an active role for these cells in regulating cellular immunity and homeostasis. Mphi-1 and Mphi-2 expressed similar levels of Toll-like receptor and dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin as microbial pattern recognition receptors. Mphi-2, unlike Mphi-1 but like other nonclassical Mphi described previously, expressed CD163 and down-modulated human leukocyte antigen and costimulatory molecules specifically upon activation. These findings demonstrate how Mphi-1/Mphi-2 polarization can differentially skew the host response toward pro- or anti-inflammatory immune responses, respectively. This is likely to be relevant for host-pathogen interactions in chronic bacterial infections and provides a model for dissecting pro- and anti-inflammatory cascades.