Schematic illustration showing the involvement of TARC, MDC, and CCL5 in microenvironment formation and RS cell growth. (A) The production of CCR5 ligands (CCL5, CCL3, and CCL4) by T cells, macrophages and fibroblasts may contribute to RS cells' proliferation (paracrine loop). (B) CCL5 produced by RS cells may represent an autocrine growth factor. (C) CCL5 produced by RS cells, together with TARC and MDC, may recruit CCR5⁺, CCR4⁺, or CCR3⁺ T cells.