All of the following represent non-specific mechanisms of body defence except:

Options

A. IgM
B. lysozyme
C. stomach acid
D. phagocytosis

Answer

To solve the question "All of the following represent non-specific mechanisms of body defense except:", we need to analyze each option provided and determine which one does not fit into the category of non-specific defense mechanisms.

### Step-by-Step Solution:

1. **Understand Non-Specific Mechanisms**: Non-specific mechanisms of body defense are those that provide a general defense against pathogens and do not target specific invaders. Examples include physical barriers (like skin), phagocytosis, lysozymes, and stomach acid.

2. **Evaluate Each Option**:
- **Option 1: IgM**: This is an immunoglobulin (antibody) that plays a role in the immune response. It is specific to particular antigens and is involved in the adaptive immune response. Therefore, it is not a non-specific mechanism.
- **Option 2: Lysozyme**: This is an enzyme that breaks down bacterial cell walls and is part of the innate immune system. It acts broadly against bacteria, making it a non-specific defense mechanism.
- **Option 3: Stomach Acid**: The acidic environment in the stomach helps kill many pathogens that enter through food and drink. This is a non-specific defense mechanism.
- **Option 4: Phagocytosis**: This is the process by which certain cells (like macrophages) engulf and digest pathogens. It is a non-specific defense mechanism.

3. **Identify the Exception**: Based on the analysis, IgM is the only option that represents a specific mechanism of defense, while the others (lysozyme, stomach acid, and phagocytosis) are non-specific.

4. **Conclusion**: Therefore, the answer to the question is **Option 1: IgM**.

### Final Answer:
**Option 1: IgM**