<prompt> MCH class 3 genes encodesComplement components C3Tumor necrosis factorIL2Beta 2microglobulin  <response>: Ref Robbins 9e p194-195 Anantha Narayana 6e p121; Harrison 17e p2047 Class III molecules include several secreted proteins with immune functions: components of the complement system such as C2, C4, and B factor, cytokines such as TNF-a, LTA, and LTB, and heat shock proteins. 