Macrophages engulf foreign material and destroy them using lysozymes. When presented with antigen by antigen presenting cells, Helper –T cells produce cytokines that activate B cells and triggers the adaptive immune response. T-helper cells determine the specificity of the adaptive response to an antigen. Cytotoxic-T-cells destroys infected cells that have displayed an antigen on the MHC I surface receptors. Suppressor T cells enable negative feedback by downregulating immunity in cases when a foreign antigen is eliminated. It also prevents autoimmunity. Plasma cells are repsosncible for the production of antibodies in the humoral immune response. Memory B and T cells ensure the immunity can remember an infectious agent and therefore can launch a faster response in case of re-infection.