Primary and secondary Immune responses The primary immune responses occurs on initial contract with a foreign and results in production of immunoglobulin M(gM) and then immunoglobulin G (IgG). If the same antigens encountered again, immuno logical memory leads to a secondary immune responses that produces a much more rapid and larger increase in specific IgG productionPrimary and secondary immune responses • The primary immune responses occurs on initial contract with a foreign and results in production of immunoglobulin M (lgM) and then immunoglobulin G (lgG). If the same antigens encountered again, immuno￾logical memory leads to a secondary immune responses that produces a much more rapid and larger increase in specific IgG production