Substances that regulate or cordinate other leucocytes are called.

Options

A. interferon
B. cytokine
C. phagocytic chemical
D. enzyme

Answer

To answer the question "Substances that regulate or coordinate other leukocytes are called," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question is asking for a specific term that describes substances involved in the regulation or coordination of leukocytes (white blood cells).

2. **Define Leukocytes**: Leukocytes, commonly known as white blood cells, are crucial components of the immune system. They help defend the body against infections and foreign materials.

3. **Identify the Function of Leukocytes**: Leukocytes have various functions, including ingesting foreign materials and coordinating immune responses. They communicate with each other and other cells in the immune system.

4. **Explore the Options**: The options given are:
- A) Interferon
- B) Cytokine
- C) Phagocytic chemical
- D) Enzyme

5. **Analyze Each Option**:
- **Interferon**: A type of cytokine that helps in the immune response but does not specifically coordinate other leukocytes.
- **Cytokine**: A broad category of signaling molecules that includes interleukins, which are specifically involved in the regulation and coordination of leukocytes.
- **Phagocytic chemical**: Refers to substances that assist in the process of phagocytosis but do not coordinate leukocytes.
- **Enzyme**: Generally involved in biochemical reactions and not specifically in the regulation of leukocytes.

6. **Select the Correct Answer**: Based on the analysis, the correct answer is **Cytokine**. This is because interleukins, which are a type of cytokine, play a significant role in regulating and coordinating the activity of leukocytes.

### Final Answer:
The substances that regulate or coordinate other leukocytes are called **Cytokines**.

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