Which among the following is an auto-immune disease?

The correct answer is Option (3) → Rheumatoid arthritis

The immune system normally attacks only foreign molecules and organisms. Sometimes, because of genetic and other unknown reasons, it attacks the body’s own cells. The damage that follows is an auto-immune disease. Rheumatoid arthritis, which affects the joints, is the book’s example.

Option (1) Asthma — Incorrect. Asthma is linked to allergy, the exaggerated response of the immune system to antigens in the environment, such as pollen, dust mites and animal dander. These are foreign substances, not the body’s own cells.

Option (2) Alzheimer's disease — Incorrect. Alzheimer’s disease is a disorder of the brain. The book names it only among the diseases for which transgenic animal models exist, not as an auto-immune disease.

Option (3) Rheumatoid arthritis — Correct. In rheumatoid arthritis the body attacks self-cells in the joints. It is the auto-immune disease named in the book.

NCERT Extract:
Auto Immunity – “Memory-based acquired immunity evolved in higher vertebrates based on the ability to differentiate foreign organisms (e.g., pathogens) from self-cells. While we still do not understand the basis of this, two corollaries of this ability have to be understood. One, higher vertebrates can distinguish foreign molecules as well as foreign organisms. Most of the experimental immunology deals with this aspect. Two, sometimes, due to genetic and other unknown reasons, the body attacks self-cells. This results in damage to the body and is called auto-immune disease. Rheumatoid arthritis which affects many people in our society is an auto-immune disease.”