Innate Immunity Overview

A pathway of complement activation that doesn't rely on antibodies. Microbial surfaces directly activate the pathway by interacting with complement proteins like C3.

A pathway of complement activation that triggers when mannose-binding lectin, a protein, binds to the mannose on microbes, leading to activation of complement proteins.

Complement activation leads to several crucial outcomes for the immune system: Cytolysis (killing of cells), Opsonization (making microbes easier to engulf), and Inflammation.

One outcome of complement activation. The creation of a Membrane Attack Complex (MAC) that punches holes in the cell membranes of microbes, causing them to burst.

One outcome of complement activation. Coating microbes with complement fragments, making them sticky and easier for phagocytes to engulf.

One outcome of complement activation. Complement fragments bind to mast cells, triggering the release of histamine, a chemical leading to inflammation and the recruitment of immune cells.

Cytokines produced by cells in response to viral infections. They stimulate neighboring cells to produce antiviral proteins that inhibit viral replication.

A cytokine produced by immune cells that activates neutrophils and macrophages to produce nitric oxide, which kills bacteria and some tumor cells.

Inflammation is a complex process that aims to destroy injurious agents, limit their effects, and repair damaged tissue. It involves three key stages: destroying the harmful agent, walling off the affected area, and repairing damaged tissues.

Acute inflammation is characterized by the presence of neutrophils, while chronic inflammation involves monocytes and macrophages. The type of inflammatory cell present reflects the stage and nature of the injury.

Chemotaxis is the process by which leukocytes (white blood cells) are attracted to the site of inflammation. Damaged cells, microbes, and neutrophils release chemical signals that guide these cells towards the injury.

During inflammation, clotting elements are brought to the injury site. This forms a barrier, preventing microbes or toxins from entering the bloodstream and spreading further.

Phagocytosis is the process where cells like neutrophils and macrophages engulf and destroy microbes or cellular debris at the inflammation site.

When repairing damaged tissues, the stroma (supporting connective tissue) is repaired by fibrosis, while the parenchyma (functioning part of the tissue) is repaired by regeneration.

Fever is a defense mechanism where vasoconstriction and shivering increase body temperature. This helps fight infection by making the environment less hospitable to microbes. As infection clears, vasodilation and sweating occur (crisis) to return to normal temperature

The complement system is a group of over 30 serum proteins produced by the liver that work to enhance the immune system's ability to destroy microbes. These proteins exist in an inactive form until they are activated.

Complex network of cells, tissues, and organs that protect the body from pathogens.

Non-specific defense system that is always present and active. It's the first line of defense against any pathogen.

Specific defense system that targets specific pathogens. It develops after exposure and has memory.

First line: Skin, mucous membranes, antimicrobial substances. Second line: Inflammation, fever, phagocytes. Third line: Humoral and cellular immunity.

Receptors on immune cells that recognize pathogen-associated molecular patterns (PAMPs) on pathogens.

Chemical messengers that regulate immune responses. They recruit cells and activate immune responses.

Skin, mucous membranes, and secretions that prevent pathogens from entering the body.

Antimicrobial substances like lysozyme and sebum that destroy pathogens.

Beneficial bacteria that live on the body and outcompete pathogens.

Elevated body temperature that inhibits pathogen growth.

Process by which phagocytes engulf and destroy pathogens.

A group of proteins that work together to destroy pathogens.

Proteins that interfere with viral replication.

Network of vessels and organs that filter lymph and house immune cells.

Small proteins produced by the body in response to microbes, they act as a first line of defense against infections. They have a broad spectrum of activity, targeting bacteria, viruses, fungi, and parasites. They work by inhibiting cell wall synthesis, forming pores in membranes, and destroying DNA/RNA.

The part of the adaptive immune system that involves antibodies produced by B lymphocytes (B cells). It's effective against pathogens and toxins found outside of cells, like bacteria and extracellular viruses.

The part of the adaptive immune system that involves T lymphocytes (T cells) which directly attack infected cells or pathogens. It effectively tackles intracellular infections like viruses.

A type of cytokine responsible for communication between white blood cells (leukocytes). They play a crucial role in coordinating various immune responses.

A type of cytokine that directs the migration of white blood cells (leukocytes) to areas where they are needed.

A type of cytokine that primarily protects against viral infections. They interfere with viral replication and alert neighboring cells about the infection.

A type of cytokine that promotes inflammation. It's essential for the immune response but excessive production can contribute to autoimmune diseases.

Substances that trigger the immune system to produce antibodies and T cells. They are often foreign molecules, like proteins or carbohydrates found on pathogens.

Antibodies are proteins produced by immune cells (B cells) that bind to specific targets, like bacteria or viruses, to neutralize them. These targets are called antigens. There are different classes of antibodies, each with a unique structure and function.

Antibodies have a Y-shaped structure, with two identical light chains and two identical heavy chains joined by disulfide bonds. The ends of the arms are called variable regions, which bind to antigens. The stem is called the constant region, which determines the antibody's class and function.

Antibodies are categorized into five classes: IgG, IgM, IgA, IgD, and IgE. Each class has a unique structure, function, and location in the body.

IgG is the most abundant antibody in the blood, making up 80% of serum antibodies. It can cross the placenta, providing passive immunity to the fetus. IgG also neutralizes toxins, activates complement, and enhances phagocytosis.

IgM is a pentamer, meaning it is made of five antibody molecules joined together. It is the first antibody produced in response to an infection, and it activates complement and agglutinates cells.

IgA is found in mucosal secretions like saliva, tears, and breast milk. It prevents pathogens from attaching to mucous membranes.

IgD is a less common antibody found on the surface of B cells. Its exact function is still being researched, but it may help regulate B cell activity.

IgE is involved in allergic reactions and is found on mast cells and basophils. It also plays a role in fighting parasitic infections.

Major histocompatibility complex genes encode glycoproteins on the cell surface that help the immune system distinguish 'self' from 'non-self'.

These proteins are found on the surface of all nucleated cells in the body, marking them as 'self'.

These proteins are only found on the surface of antigen-presenting cells (APCs) like B cells, dendritic cells, and macrophages, assisting with antigen presentation to T cells.

Cells that engulf and degrade microbes, then present the antigens to T cells using MHC II molecules.

The primary APCs, found in various locations, engulf and degrade microbes and are crucial for initiating adaptive immune responses.

They can be activated by cytokines or by engulfing antigens, and then present the antigens to T cells using MHC II molecules.

These cells are also known as T helper cells. They bind to MHC class II molecules and antigens on B cells and APCs, initiating a cascade of immune responses.

A type of T helper cell that produces IFN-y, activating macrophages and boosting other immune responses.

A type of T helper cell that produces IgE, activating B cells to produce IgE and eosinophils, primarily involved in allergic responses.

A type of T helper cell that produces IL-17, which plays a key role in inflammation.

These cells, formally known as T suppressor cells, help suppress T cells that target self antigens, preventing autoimmune reactions.

These cells bind to MHC class I molecules on infected cells and release substances that induce apoptosis (programmed cell death) of the infected cell.

These cells, part of the innate immune system, destroy cells that lack MHC class I molecules, like virus-infected and tumor cells.

The ability of the immune system to remember a prior infection and mount a faster and stronger response upon subsequent exposure.

Characterized by a faster and stronger response compared to the primary response, due to the presence of memory cells.