Among the five classes of immunoglobulins in humans, the one that is secretory in nature is

Options

A. Ig A
B. Ig E
C. Ig M
D. Both a and c

Answer

To solve the question about which class of immunoglobulins in humans is secretory in nature, we can follow these steps:

### Step 1: Understand the Classes of Immunoglobulins
There are five classes of immunoglobulins (antibodies) in humans:
1. IgA
2. IgD
3. IgG
4. IgE
5. IgM

### Step 2: Identify the Secretory Nature of Immunoglobulins
Secretory immunoglobulins are those found in bodily secretions such as mucus, tears, saliva, and breast milk. These antibodies play a crucial role in mucosal immunity.

### Step 3: Focus on IgA
Among the five classes, IgA is primarily known for its secretory function. It is found in high concentrations in secretions like:
- Mucus (in the gastrointestinal and respiratory tracts)
- Tears
- Saliva
- Breast milk

### Step 4: Consider IgM
IgM is also present in secretions but is primarily known for its role in the initial immune response and is not typically classified as a secretory antibody in the same way as IgA.

### Step 5: Review the Options
Given the options:
- A: IgA
- B: IgD
- C: IgM
- D: Both A and C

Since IgA is the main secretory immunoglobulin, and IgM is also found in secretions but not primarily classified as secretory, we conclude that:
- Option A (IgA) is correct.
- Option C (IgM) is also correct in a broader context.
- Therefore, Option D (Both A and C) is the most accurate answer.

### Final Answer
The correct answer is **D: Both A and C**.

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