Memory cells are

Options

A. Cells responsible for immunologic memory
B. Antigens
C. Cells of cerebrum
D. Cells responsible for memory in brain

Answer

**Step-by-Step Solution:**

1. **Understanding Memory Cells**: Memory cells are a type of immune cell that play a crucial role in the body's defense mechanism. They are formed after an initial infection and are responsible for remembering past infections.

2. **Function of Memory Cells**: When a person is infected by a virus, their immune system produces antibodies to fight off the infection. After the infection is cleared, some of these immune cells become memory cells. If the same virus infects the person again, these memory cells quickly recognize the virus and initiate a faster and more effective immune response.

3. **Analyzing the Options**:
- **Option A: Cells responsible for immunologic memory**: This option correctly describes memory cells as they are indeed responsible for retaining the memory of past infections.
- **Option B: Antigen**: Antigens are substances that trigger an immune response, but they are not memory cells themselves.
- **Option C: Cells of cerebrum**: This option refers to brain cells, which are unrelated to the immune system and memory cells.
- **Option D: Cells responsible for memory in brain**: This option also pertains to brain function rather than the immune system.

4. **Conclusion**: Based on the analysis of the options, the correct answer is **Option A: Cells responsible for immunologic memory**. This option accurately defines the role of memory cells in the immune system.