Immunity Types, Cells, and Responses: A Comprehensive Review

What are the two types of immunity?

Nonspecific (innate) immunity and specific (acquired) immunity.

What is the primary function of the innate immune system?

To provide a first line of defense against pathogens, present from birth.

What are the external mechanisms of the innate immune system?

Skin, gastrointestinal tract, respiratory tract, urinary and reproductive tracts, and tear production.

What role does skin play in the immune system?

It serves as the primary physical barrier to invasion and contains lysozyme in secretions.

How does the gastrointestinal tract contribute to nonspecific immunity?

It has an extreme acid environment (HCl) and intestinal bacteria that provide protection.

What are the internal mechanisms of the innate immune system?

Phagocytic cells, NK cells, fever, interferons, and complement proteins.

What are phagocytic cells and their role in the immune system?

Cells like neutrophils, monocytes, and macrophages that engulf and digest pathogens.

What is chemotaxis in the context of the immune response?

The attraction of neutrophils and monocytes to the site of infection by chemicals called chemokines.

What is diapedesis?

The movement of white blood cells through small openings in capillary walls to reach the site of infection.

What triggers a fever in the immune response?

Endotoxins from gram-negative bacteria stimulate cytokine release, resetting the hypothalamus to a higher temperature.

What are interferons and their function?

Proteins released by virus-infected cells that alert neighboring cells and inhibit viral replication.

What is the role of local inflammation in the immune response?

It is a defensive mechanism initiated by phagocytosis that attracts phagocytic cells to the site of injury or infection.

What are the signs of local inflammation?

Redness, heat, swelling, and pain due to increased blood flow and immune cell activity.

What are the two types of specific/adaptive immunity?

Humoral (antibody-mediated) immunity involving B lymphocytes and cell-mediated immunity involving T lymphocytes.

Where do B and T lymphocytes originate?

B lymphocytes mature in the bone marrow, while T lymphocytes mature in the thymus.

What is the function of B lymphocytes?

To secrete antibodies and kill infected cells at a distance.

What is the significance of memory in the immune response?

It allows the immune system to remember previous encounters with pathogens and respond more rapidly.

What are PAMPs and their role in the immune system?

Pathogen-associated molecular patterns recognized by phagocytic cells to identify invaders.

What are the three major groups of phagocytic cells?

Neutrophils, monocytes (which become macrophages), and organ-specific phagocytes like microglia and Kupffer cells.

What is the role of cytokines in the immune response?

They are signaling molecules that mediate and regulate immunity, inflammation, and hematopoiesis.

What stimulates plasma cells to secrete antibodies?

Exposure to an appropriate antigen.

What are memory cells?

Long-lived cells that respond quickly upon subsequent exposure to the same antigen.

What is the role of T-lymphocytes in cellular immunity?

They must contact victim cells to mediate immune responses.

What are the three subpopulations of T-lymphocytes?

Killer T-cells, Helper T-cells, and Regulatory T-cells.

What is the function of antigen-presenting cells?

They present antigens to T cells on their membrane.

Which cells are considered antigen-presenting cells?

Dendritic cells and macrophages.

What is the function of MHC proteins?

They serve as identification tags that label cells as belonging to the body.

Where is MHC-1 found and what does it do?

On the surface of all nucleated cells (except RBCs), presenting antigens to CD8+ T-cells.

Where is MHC-2 found and what does it do?

On the surface of APCs, presenting antigens to CD4+ T-cells.

What is the primary function of Killer T-cells?

To defend against viral and fungal infections and destroy infected cells.

How do Killer T-cells destroy infected cells?

By secreting perforins that rupture the victim cell's membrane and inducing apoptosis.

What is the role of Helper T-cells?

To stimulate B-lymphocyte and Killer T-lymphocyte activity.

What do Regulatory T-cells do?

They inhibit T cell and B cell activities and moderate the immune response.

What is the complement system?

A group of 30 proteins that contribute to both nonspecific and innate immunity.

How does the complement system clear pathogens?

By triggering inflammation, immune clearance via Ag-Ab complex, and opsonizing pathogens.

What are antigens?

Foreign substances that stimulate the immune system to produce antibodies.

What are antibodies?

Immunoglobulins formed by four polypeptide chains linked by S-S bonds.

What is the difference between active and passive immunity?

Active immunity involves the formation of antibodies by the host, while passive immunity involves the transfer of antibodies from a donor.

What is the primary response in active immunity?

The first exposure to a pathogen, resulting in a latent period before antibodies appear.

What is the secondary response in active immunity?

A more rapid antibody production upon subsequent exposure to the same antigen.

What are autoimmune diseases?

Conditions where the immune system does not recognize self-antigens, leading to inflammation and organ damage.

What causes allergies?

An overreaction of the immune system to typically harmless antigens.

What is immediate hypersensitivity?

An allergic reaction characterized by the production of IgE antibodies and the release of histamine.