The immune system does not normally attack on immature germ cells because

Options

A. They are recognized as ''self'' structures
B. They do not have any antigens and their cell membrane
C. These cells are protected by the blood testis barrier
D. The acrosome covers many antigens that into ovum would be recognized as foreign

Answer

To answer the question, "The immune system does not normally attack immature germ cells because," we need to analyze the provided options and understand the underlying biological concepts.

### Step-by-Step Solution:

1. **Understanding Immature Germ Cells**: Immature germ cells are the precursor cells that eventually develop into sperm or eggs. They are present in the gonads (testes in males and ovaries in females).

2. **Immune System's Role**: The immune system is responsible for identifying and attacking foreign substances, including pathogens and cells that do not belong to the body.

3. **Options Analysis**:
- **Option 1**: They are recognized by self-structures.
- **Option 2**: They do not have any antigen on their surface.
- **Option 3**: They are protected by the blood-testes barrier.
- **Option 4**: The acrosome covers many antigens into the ovum and would recognize it as foreign.

4. **Eliminating Incorrect Options**:
- **Option 3** (blood-testes barrier) and **Option 4** (acrosome) do not directly relate to the recognition of immature germ cells by the immune system. Thus, these options can be eliminated.
- **Option 2** suggests that immature germ cells do not have any antigens on their surface, which is incorrect because they do have self-antigens.

5. **Correct Option**: The remaining option is **Option 1**: "They are recognized by self-structures." This means that the immune cells (B and T cells) recognize these immature germ cells as part of the body (self), leading to a state of tolerance.

6. **Tolerance Mechanism**: The immune system has a mechanism known as "tolerance," where it does not attack cells that are recognized as self. This is crucial for preventing autoimmune reactions where the body attacks its own cells.

### Conclusion:
The immune system does not normally attack immature germ cells because they are recognized by self-structures.