Read the following statements and select the right option :
I. The spleen is a large bean-shaped organ, which mainly contains lymphocytes and phagocytic cells.
II. The principal of vaccination is based on the property of memory of the immune system.
III. The graft rejected or failure of organ transplantation is due to cell-mediated immunity .
IV. The yellowish fluid colostrum has an abundant amount of lgA antibodies which provide active immunity to newborn babies.

Options

A. I,II,III are correct
B. II, III, IV are correct
C. II and IV are correct
D. Only II is correct

Answer

To solve the question, we need to evaluate each of the four statements provided and determine which ones are correct.

### Step 1: Analyze Statement I
**Statement I:** "The spleen is a large bean-shaped organ, which mainly contains lymphocytes and phagocytic cells."

- The spleen is indeed a large organ that plays a crucial role in the immune system. It contains lymphocytes (a type of white blood cell) and phagocytic cells (cells that engulf and digest pathogens). Additionally, it acts as a reservoir for red blood cells and helps in their recycling.
- **Conclusion:** This statement is correct.

**Hint for Step 1:** Remember that the spleen is involved in both immune responses and the recycling of red blood cells.

### Step 2: Analyze Statement II
**Statement II:** "The principle of vaccination is based on the property of memory of the immune system."

- Vaccination introduces a weakened or inactive form of a pathogen into the body, which stimulates the immune system to produce antibodies and memory cells. These memory cells remain in the body and provide a faster and stronger response upon subsequent exposure to the same pathogen.
- **Conclusion:** This statement is also correct.

**Hint for Step 2:** Focus on how vaccinations prepare the immune system for future encounters with pathogens.

### Step 3: Analyze Statement III
**Statement III:** "The graft rejected or failure of organ transplantation is due to cell-mediated immunity."

- Graft rejection is indeed primarily mediated by T lymphocytes, which are part of the cell-mediated immune response. When a foreign tissue (graft) is introduced, the immune system may recognize it as non-self and mount a response against it.
- **Conclusion:** This statement is correct.

**Hint for Step 3:** Recall the role of T cells in recognizing and responding to foreign tissues in graft rejection.

### Step 4: Analyze Statement IV
**Statement IV:** "The yellowish fluid colostrum has an abundant amount of IgA antibodies which provide active immunity to newborn babies."

- Colostrum is the first milk produced by mammals after giving birth and is rich in antibodies, particularly IgA. However, it provides passive immunity, not active immunity, because the antibodies are transferred from the mother to the baby rather than produced by the baby’s own immune system.
- **Conclusion:** This statement is incorrect.

**Hint for Step 4:** Distinguish between active and passive immunity; active immunity is generated by the individual's own immune response.

### Final Conclusion
Based on the analysis:
- Statements I, II, and III are correct.
- Statement IV is incorrect.

Thus, the correct option includes statements I, II, and III.

### Final Answer
The right option is: **I, II, and III are correct.**