Name the disorder in which both T-cells and B-cells are absent.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a disorder characterized by the absence of both T-cells and B-cells, which are types of lymphocytes crucial for the immune response.

2. **Identifying T-cells and B-cells**: T-cells and B-cells are types of white blood cells (WBCs) that play significant roles in the immune system. T-cells help in directly killing pathogens and assisting B-cells, while B-cells are responsible for producing antibodies.

3. **Recognizing the Importance of Lymphocytes**: Both T-cells and B-cells are essential for a functioning immune system. Their absence results in a severely compromised immune response, making the body vulnerable to infections.

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