**Core Concept:** Cell adhesion molecules (CAMs) are proteins that facilitate the attachment of cells to each other or to extracellular matrix components. They play a crucial role in various physiological and pathological processes, including tissue development, immune response, and inflammation. Calcium ions are essential for the proper functioning of some CAMs.

**Why the Correct Answer is Right:** Calcium ions are involved in the regulation of cell-cell adhesion through their interaction with calcium-binding proteins, such as cadherins. Cadherins are a family of cell adhesion molecules that are involved in various physiological processes, including tissue development, wound healing, and immunological responses. The binding of calcium ions to cadherins stabilizes the cell-cell contacts and maintains the structural integrity of tissues.

**Why Each Wrong Option is Incorrect:**

A. Integrins are transmembrane proteins involved in cell adhesion but are not calcium-mediated.
B. Selectins are calcium-independent CAMs involved in leukocyte adhesion and rolling.
C. Immunoglobulins (Ig) are calcium-dependent CAMs involved in cell-cell and cell-matrix interactions, but they are not specifically calcium-mediated cell adhesion molecules.
D. Neural cell adhesion molecules (NCAMs) are calcium-dependent CAMs involved in neuronal development and synapse formation, but they are not exclusively calcium-mediated CAMs.

**Clinical Pearl / High-Yield Fact:** Calcium-mediated cell adhesion molecules play a vital role in various physiological processes, including tissue development, immune response, and inflammation. Adequate understanding of these molecules and their functions is essential for medical students, residents, and practicing physicians alike, as it helps to grasp the fundamental principles of cell biology and tissue organization.

**Correct Answer:** D. Neural cell adhesion molecules (NCAMs) are calcium-dependent CAMs involved in neuronal development and synapse formation, but they are not exclusively calcium-mediated CAMs.