Comprehensive Immunology: Main Functions, Cells, and Responses

What is the main function of the immune system?

To distinguish self (host molecules) from non-self (foreign molecules) and defend the body against pathogens.

What happens in autoimmune diseases?

The immune system mistakenly attacks the body's own cells or tissues.

What is immunodeficiency?

A condition where the immune system fails to adequately protect an organism.

Two main types of immunity

Innate (natural) immunity and Adaptive (acquired) immunity.

Innate immunity

The body's first line of defense; nonspecific and present at birth.

Adaptive immunity

A specific immune response that develops after exposure to a pathogen; has memory.

Physical barriers of innate immunity

Skin and mucous membranes, which prevent pathogen entry.

Examples of innate immune cells

Macrophages, neutrophils, dendritic cells, eosinophils, basophils, mast cells, and natural killer (NK) cells.

What do toll-like receptors (TLRs) do?

Detect pathogens on immune cell surfaces and trigger cytokine release.

What are cytokines?

Signaling proteins that recruit immune cells to infection sites.

Four classic signs of inflammation

Redness, heat, pain, and swelling.

Function of inflammation

Increases blood flow, recruits immune cells, and helps repair tissue.

Complement system

A group of proteins in blood that, when activated, trigger a biochemical cascade enhancing immune response.

Three effects of the complement system

Opsonization, inflammation, and cell lysis.

Two features of adaptive immunity

Specificity and memory.

Where do B and T cells mature?

B cells in bone marrow; T cells in thymus.

Function of B cells

Produce antibodies that bind to specific antigens.

Function of T cells

Attack infected or abnormal cells; regulate immune responses.

What are antibodies?

Proteins made by B cells that specifically bind to antigens.

Parts of an antibody

Two light and two heavy chains with variable and constant regions.

What is an epitope?

The specific region of an antigen recognized by an antibody.

What is neutralization?

When antibody binding disables a microorganism directly.

Types of antibodies

IgG, IgA, IgM, IgE, and IgD (each with specific roles in immunity).

What is clonal selection?

Process where only B or T cells specific to an antigen multiply to form a clone.

What is immunological memory?

The immune system's ability to respond faster to a pathogen it has encountered before.

What is a vaccine?

A preparation that stimulates immune memory without causing disease.

Types of vaccines

Attenuated (weakened), inactivated (killed), and conjugate (combined with another antigen).

Types of T cells

Helper T cells, cytotoxic T cells, and regulatory T cells.

Helper T cell function

Activate other immune cells by releasing cytokines.

Cytotoxic T cell function

Kill infected or abnormal cells directly.

Regulatory T cell function

Suppress or regulate immune responses to prevent overreaction.

What is the Major Histocompatibility Complex (MHC)?

Genes encoding proteins that present antigens on cell surfaces.

MHC Class I

Found on all nucleated cells; recognized by cytotoxic T cells.

MHC Class II

Found on macrophages, dendritic cells, and B cells; recognized by helper T cells.

T Cell Receptor (TCR)

Protein on T cells that recognizes antigens bound to MHC proteins.

How do T cells develop self-tolerance?

T cells that strongly react to self-antigens are eliminated during maturation.

What happens if self-tolerance fails?

Autoimmune diseases develop.