Protein which is secreted by virus infected cell and form cytokine barrier is :-

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a specific protein that is secreted by virus-infected cells and forms a cytokine barrier.

2. **Identifying the Protein**: The protein secreted by virus-infected cells is known as **interferon**.

3. **Function of Interferon**: Interferons are crucial in the immune response. When a cell is infected by a virus, it releases interferons to signal neighboring healthy cells to enhance their antiviral defenses.

4. **Role in Cytokine Barrier**: By doing so, interferons help establish a barrier that protects nearby cells from becoming infected by the virus. This is referred to as the cytokine barrier.

5. **Conclusion**: Therefore, the protein that is secreted by virus-infected cells and forms a cytokine barrier is **interferon**.

**Final Answer**: Interferon

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