Though monocyte levels have not been observed to fluctuate after CPB, the surface expression of some receptors is altered, with a reduction in the expression of TLR2/TLR4; reduced expression of TLR2 has been associated with the occurrence of systemic inflammatory response syndrome (SIRS) and pneumonia in the postoperative period [150]. The gene discussed is TLR4; the disease is systemic inflammatory response syndrome.