**Core Concept**
Memory cells, also known as memory T cells or memory B cells, are a type of lymphocyte that retains a "memory" of a specific antigen, allowing for a more rapid and effective immune response upon subsequent exposure. This concept is crucial in understanding vaccine efficacy and the body's ability to combat recurring infections.

**Why the Correct Answer is Right**
Memory cells are primarily provided by the differentiation of naive T cells and B cells into effector cells, which then undergo apoptosis and leave behind a subset of long-lived memory cells. These memory cells are capable of recognizing and responding to the same antigen by proliferating and differentiating into effector cells, thereby providing long-term immunity. The process of memory cell formation involves the activation of T cells and B cells, which then undergo clonal expansion and differentiation into effector cells and memory cells.

**Why Each Wrong Option is Incorrect**
**Option A:** While vaccines can stimulate the production of memory cells, they are not the primary source of memory cells. Vaccines work by presenting antigens to the immune system, which then mounts a response and produces memory cells.
**Option B:** Antibodies produced in response to an infection are not memory cells themselves, but rather a product of memory B cells. While antibodies provide short-term protection, memory cells are responsible for long-term immunity.
**Option C:** Dendritic cells play a crucial role in the activation and differentiation of naive T cells and B cells into effector cells and memory cells, but they are not the primary providers of memory cells.

**Clinical Pearl / High-Yield Fact**
Memory cells are responsible for the phenomenon of "herd immunity," where a sufficient percentage of a population is immune to a disease, thereby protecting those who are not immune, such as the young, elderly, or immunocompromised.

**Correct Answer: C. Dendritic cells**