Correct option is A
Explanation-
Option a – The white blood cell proteins recognized by endothelial cell integrins are called ICAM or VCAM.
ICAM (Intercellular Adhesion Molecule) and VCAM (Vascular Cell Adhesion Molecule) are found on the surface of endothelial cells (lining of blood vessels).
These molecules are recognized by integrins present on white blood cells (WBCs).
So, the correct version should be - Endothelial ICAM and VCAM are recognized by integrins on white blood cells.
This statement gets the direction of binding backwards, which makes it factually incorrect.
Option b – .These are called Ig superfamily because they contain one or more extracellular Ig-like domains that are characteristic of antibody molecules.
Yes, Ig superfamily proteins all have immunoglobulin-like (Ig-like) domains in their extracellular regions. This structure is similar to antibody domains, which is why they’re called the Ig superfamily.
This is correct.
Option c – ICAM and VCAM mediate heterotrophic binding to integrin, whereas N-CAM (neural cell adhesion molecule) mediates homotrophic binding.
Heterotropic binding - ICAM/VCAM bind to integrins on other cells → different proteins.
Homotropic binding - NCAM (Neural CAM) binds to other NCAM molecules → same protein.
This is correct.
Option d - They contain large quantities of sialic acid which inhibit adhesion by charge-based repulsion contributing to fine tuning of cell-cell adhesion.
Some Ig superfamily proteins like NCAM can be highly sialylated, especially in the nervous system. This sialic acid adds negative charge, reducing adhesion between cells when needed.
Though not true for all Ig superfamily proteins, it is correct for specific cases, so the statement is acceptable.
Since the option a is the only incorrect statement among all the others that makes it a correct answer.
So, the correct answer is option a - The white blood cell proteins recognized by endothelial cell integrins are called ICAM or VCAM.
