Read the following list carefully ........ Neutrophils, erythrocytes, monocytes, macrophages, B lymphocyte , NK cells, T lymphocytes, thrombocytes.
How many of the above cells constitute cellular barrier of innate immunity ?

Options

A. Three
B. Four
C. Five
D. Six

Answer

To determine how many of the listed cells constitute the cellular barrier of innate immunity, we can analyze each cell type in the context of innate immunity.

### Step-by-Step Solution:

1. **Understanding Innate Immunity**:
- Innate immunity is the body's first line of defense against pathogens and is non-specific. It is present from birth and includes various barriers, including physical, physiological, and cellular barriers.

2. **Identifying the Cellular Components**:
- The cells involved in innate immunity include:
- **Neutrophils**: These are white blood cells that are part of the innate immune response and are known for their role in phagocytosis, where they engulf and destroy pathogens.
- **Monocytes**: These are also white blood cells that differentiate into macrophages and dendritic cells, playing a crucial role in the immune response.
- **Macrophages**: These are derived from monocytes and are essential phagocytes that engulf and digest pathogens.
- **Natural Killer (NK) Cells**: These cells play a critical role in the innate immune response by targeting and destroying infected or cancerous cells.

3. **Cells Not Involved in Innate Immunity**:
- **Erythrocytes (Red Blood Cells)**: These cells are responsible for oxygen transport and do not play a role in immunity.
- **B Lymphocytes**: These are part of the adaptive immune system and are involved in antibody production.
- **T Lymphocytes**: These are also part of the adaptive immune system and are involved in cell-mediated immunity.
- **Thrombocytes (Platelets)**: These are involved in blood clotting and do not have a direct role in the immune response.

4. **Counting the Innate Immune Cells**:
- From the list, the cells that constitute the cellular barrier of innate immunity are:
- Neutrophils
- Monocytes
- Macrophages
- NK Cells
- This gives us a total of **4 cells** that are part of the innate immune response.

### Final Answer:
The number of cells from the list that constitute the cellular barrier of innate immunity is **4**.