Final answer:
The pair of adhesion molecules and their ligands provided in the question are all matched correctly, including LFA-1 with ICAM-1, CCR7 with CCL21, CD28 with B7, and CTLA4 also with B7.
Step-by-step explanation:
The correct option is e:
Each pair provided in the options, such as LFA-1 : ICAM-1, CCR7 : CCL21, CD28 : B7, and CTLA4 : B7, is matched correctly. These pairs participate in vital processes of the immune system such as initiating immune responses, guiding cell migration, and modulating T-cell activity.
LFA-1, also known as leukocyte function-associated antigen-1, indeed binds to ICAM-1 (Intercellular Adhesion Molecule 1), which plays a critical role in the immune system by acting at the level of the vascular endothelium to capture leukocytes. CCR7, a chemokine receptor, recognizes the chemokine CCL21 as its ligand, which helps direct the migration of immune cells. CD28 is a costimulatory molecule on T cells that binds to its ligand B7, providing an essential signal for T cell activation. Similarly, CTLA4 (Cytotoxic T-Lymphocyte-Associated protein 4) also binds to B7 and functions as an inhibitory receptor that downregulates the immune response.