Question

Humoral immunity is due to
(a) T-lymphocytes
(b) L-lymphocytes
(c) P-lymphocytes
(d) B-lymphocytes / plasma cells

Answer 1

Hint: Humoral immunity is so- called because the substances present in humor or body fluids are involved. It's also called antibody- mediated immunity. The cells involved in humoral immunity originate and mature in the bone marrow.

Complete step by step answer:
The humoral immunity is mediated by the B-lymphocytes which matures in the bone marrow. B cells have the primary purpose of developing antibodies to soluble antigens. B- cell antigen recognition is not the only factor required for B- cell activation (a combination of clonal proliferation and plasma- cell terminal differentiation). The plasma cells then develop antigen- fighting antibodies.
The B cells are of two kinds, memory B cells, and regulatory B cells.
Memory B cells circulate throughout the body when they encounter a foreign material to begin a rapid response to the antibody. For decades they stay in the body and become memory cells, which recognize previously identified antigens and help the immune system respond more rapidly to potential attacks.
Regulatory B cells or Bregs in healthy people make up around 0.5% of all B cells. They do have a critical role to play, although small in number. Bregs have beneficial anti- inflammatory effects in the body and resist inflammatory lymphocytes.
One of the main components of the adaptive immune system is the T cells (also called T lymphocytes) . Their functions are to destroy infected host cells directly, activate other immune cells, generate cytokines, and control the immune response.
So, the correct answer is, '(d) B-lymphocytes or plasma cells'.

Note:
The adaptive immune system has two primary pathways of immunity, such as humoral and cellular.
- In humoral immunity, B cells can divide into plasma B cells that can develop antibodies against a particular antigen with the help of helper T cells. The humoral immune system deals with pathogenic antigens that circulate openly or outside of the cells infected. Antibodies formed by the B cells can bind to, neutralize, or induce lysis or phagocytosis of antigens.
- Within infected cells, cellular immunity exists and is mediated by T lymphocytes. On the cell surface or on an antigen- presenting cell, the pathogen's antigens are expressed. T cells are involved in cell- mediated immunity, while humoral immunity is mainly the responsibility of B cells. The key difference between T cells and B cells is that viral antigens can only be recognized by T cells outside the infected cells, while surface antigens of bacteria and viruses can be recognized by B cells. Both B cells and T cells originate from the bone marrow, while B cells mature in the bone marrow and T cells mature in the thymus.