Question

What are lymphocytes? Comment upon two special types of lymphocytes present in our body.

Hint:

One type releases antibodies into the blood; the other type acts directly on infected cells.

Answer 1

Step 1: Define lymphocytes.
Lymphocytes are a type of white blood cell that forms the core of the body's specific (adaptive) immune response, meaning they target particular pathogens rather than attacking everything in a general way.

Step 2: Describe B-lymphocytes.
B-lymphocytes (B-cells) mature in the bone marrow. When they meet a matching antigen, they multiply and turn into plasma cells that secrete large amounts of antibodies into the blood, giving humoral immunity.

Step 3: Describe T-lymphocytes.
T-lymphocytes (T-cells) mature in the thymus gland. Rather than releasing free antibodies, they act directly, for example by killing infected body cells or by helping to activate other immune cells, giving cell mediated immunity.

Final Answer:
Lymphocytes are white blood cells driving adaptive immunity; B-lymphocytes produce antibodies (humoral immunity), and T-lymphocytes act directly on infected cells (cell mediated immunity).