Final answer:
CD antigens are specific proteins found on the surface of lymphocytes and other immune cells. They play a role in antigen recognition, activation, and regulation of immune responses.
Step-by-step explanation:
Lymphocytes, a type of white blood cell, are involved in various functions of the immune system. They play a crucial role in recognizing and responding to antigens, which are substances that trigger an immune response. CD antigens, also known as cluster of differentiation antigens, are specific proteins found on the surface of lymphocytes and other immune cells. They help in antigen recognition, activation, and regulation of immune responses. For example, CD4 and CD8 are two types of CD antigens found on T cells, a type of lymphocyte, and they are involved in immune cell communication and coordination. CD19 is a CD antigen found on B cells, another type of lymphocyte, and it plays a role in B cell activation and antibody production.