Final answer:
T cells and B cells use unique receptors to bind antigens with varying affinities, termed high or low affinity, which are determined by the variable regions of the receptor. This receptor diversity allows for recognition of numerous antigens, and T cell activation depends on antigen processing and presentation by MHC molecules.
Step-by-step explanation:
In the realm of immunology, both T cells and B cells recognize specific antigens using unique receptor molecules on their surface, which work akin to a lock-and-key mechanism. These receptors are highly variable, allowing the immune system to recognize an immense diversity of pathogens. For any given antigen, there will be a range of T cell receptors with varying affinities; some receptors will bind the antigen tightly, known as high affinity, and others will bind weakly, known as low affinity. The variable regions at the terminal ends of a T cell receptor's two chains determine this antigenic specificity.
T cells and B cells are similar in their singular expression of a specific antigen receptor, and both require activation by antigen-presenting cells to initiate an immune response. The diversity in T cell receptors arises from the different amino acid sequences in their variable domains, which is essential for the recognition of a wide array of antigens. Activation of T cells involves the recognition of processed antigens that are presented by MHC molecules on other cells.