To answer the question regarding the roles of the immune system, we will analyze each option step by step.
### Step 1: Analyze the Role of the Immune System in Recognition of Foreign Antigens
The immune system is crucial for identifying foreign antigens, which are substances that the body recognizes as non-self, such as pathogens (bacteria, viruses) and toxins. Upon recognizing these antigens, the immune system activates various immune responses, including the production of antibodies.
**Hint:** Think about how the immune system distinguishes between self and non-self entities.
### Step 2: Evaluate the Immune Response and Memory
Once the immune system recognizes an antigen, it responds by producing specific antibodies. Additionally, it has a memory function, allowing it to remember the encountered antigens. This memory enables a faster and more efficient response upon subsequent exposures to the same antigen.
**Hint:** Consider how vaccinations work to provide long-term immunity.
### Step 3: Consider Allergic Reactions
The immune system is also responsible for allergic reactions, which occur when it overreacts to harmless substances (allergens) as if they were harmful pathogens. This hypersensitivity can lead to various allergic symptoms.
**Hint:** Recall examples of common allergens and the body's exaggerated response to them.
### Step 4: Examine Autoimmune Diseases
In autoimmune diseases, the immune system mistakenly identifies the body’s own cells as foreign and mounts an immune response against them. This can lead to tissue damage and various health issues.
**Hint:** Think about diseases like rheumatoid arthritis or lupus, where the immune system attacks the body itself.
### Step 5: Assess Organ Transplantation
During organ transplantation, the immune system may recognize the transplanted organ as foreign tissue. This can trigger an immune response against the organ, which is why immunosuppressive drugs are often required to prevent rejection.
**Hint:** Consider why transplant recipients need to take medication to suppress their immune response.
### Conclusion
Based on the analysis of all the options, the immune system plays an important role in:
- (a) Recognition of foreign antigens
- (b) Responding to antigens and remembering them
- (c) Allergic reactions
- (d) Autoimmune diseases
- (e) Organ transplantation
Thus, the correct answer is that the immune system is involved in all the mentioned roles (A, B, C, D, E).
**Final Answer:** All of the above options (A, B, C, D, E) are correct.
