Question: Define antigens, antigenic determinants, and antibodies. Describe how each affects the adaptive defenses. Differentiate complete antigens and partial antigens (haptens). Explain the role of MHC proteins in antigen presentation. Compare and contrast the origin, maturation process, and general functions of B and T lymphocytes. List and describe the three main types of antigen-presenting cell. Explain how the innate and adaptive immune systems communicate with one another. Need Assignment Help?