Question

Discuss the major differences between humoral and cell-mediated immunity, including cell types involved and the end result of the immune process. Why is it essential to have both a humoral as well as a cell-mediated immune response in order to have a fully competent immune system?

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Answer 1

Meaning

The humoral immunity is associated with the B-lymphocytes and is responsible for destroying the pathogens by producing antibodies against it.

The cell-mediated immunity is associated with the T-lymphocytes and is responsible for destroying the pathogens or microorganism which have invaded the cells.

Mediated by

Humoral immunity is intimately associated with B-lymphocytes, T-lymphocytes and macrophages.

These are associated with T-lymphocytes, helper T cells, natural killer cells and macrophages.

Antibodies	Present.	Absent.
Function	1. It plays a major role in recognizing antigen or any foreign particle and in producing antibodies against it. 2. Humoral immunity is known for working against extracellular pathogens.	1. Cell-mediated immunity is related to T-lymphocytes, which work by identifying viruses and microorganisms,thus destroying them by the cell lysis or phagocytosis or pinocytosis. 2. It is known for working against intracellular pathogens.
Secretes	It secrets antibodies.	It secretes cytokines.
Action against pathogen	Humoral immunity is rapid or quick in their response.	The Cell-mediated immunity show delay though permanent action against any pathogens.
Hypersensitivity	It mediates hypersensitivity type I, II and III.	Cell-mediated is the delayed in response and mediates hypersensitivity type IV.
Rejections	Humoral immunity is involved in the early stage of graft rejections due to the formation of antibodies.	Cell-mediated immunity is involved in the rejection of organ transplants

2. The cells of the immune system can be categorized as lymphocytes (T-cells, B-cells and NK cells), neutrophils, and monocytes/macrophages. These are all types of white blood cells

3.

Both humoral and cell mediated responses are essential for antiviral defense. The contribution of each varies, depending on the virus and the host. Antibodies generally bind to virus particles in the blood and at mucosal surfaces, thereby blocking the spread of infection. In contrast, T cells recognize and kill infected cells.

A key feature of the adaptive immune system is memory. Repeat infections by the same virus are met immediately with a strong and specific response that usually effectively stops the infection with less reliance on the innate system. When we say we are immune to infection with a virus, we are talking about immune memory. Vaccines protect us against infection because of immune memory. The first adaptive response against a virus – called the primary response – often takes days to mature. In contrast, a memory response develops within hours of infection. Memory is maintained by a subset of B and T lymphocytes called memory cells which survive for years in the body. Memory cells remain ready to respond rapidly and efficiently to a subsequent encounter with a pathogen. This so-called secondary response is often stronger than the primary response to infection. Consequently, childhood infections protect adults, and immunity conferred by vaccination can last for years.