Biology Unit 4 AOS 1

Disease

Refers to the impaired functioning of cells or processes within the body.

Major histocompatibility complex (MHC) markers

A group of proteins present on the surface of all self-cells that enables the immune system to distinguish it from non-self material.

Major histocompatibility complex class (MHC Class I) markers

Expressed on all nucleated cells in the body. These mark cells as 'self' so that the immune system doesn't attack them.

Major histocompatibility complex class II  (MHC Class II) markers 

Expressed on antigen-presenting cells, which interact with T helper cells in the process of antigen-presentation.

Autoimmune disease

A disease in which an individual's immune system initiates an immune response against their own cells.

Allergic reaction

An overreaction of the immune system to a non-pathogenic antigen.

Cellular pathogen

A pathogen that has a cellular structure and exhibits the processes of a living organism.

Non-cellular pathogen

A pathogen that neither has a cellular structure nor exhibits the processes of a living organism.

Lysis

The disintegration or rupturing of a cell.

Hyphae

Branching filaments of a fungus which help absorb nutrients from the environment.

Parasite

An organism that lives in or on another organism, usually deriving nutrition from the host organism.

Innate immune system (non-specific immune system)

A component of the immune system that is composed of generalised and non-specific defences and/or responses to pathogens.

First line of defence

A component of the innate immune system characterised by the presence of physical, chemical, and microbiological barriers to keep pathogens out of the host organism.

Second line of defence

A component of the innate immune system characterised by the non-specific response to injury and/or pathogens by a variety of cells and molecules.

Non-specific

Describes a component of the immune system that responds the same way to all pathogens

Physical barrier

A component of the first line of defence that features solid or fluid obstacles that block pathogen entry such a skin or mucus.

Chemical barrier

A component of the first line of defence that features the use of enzymes, toxins, and acids to protect against pathogen invasion.

Cuticle

A waxy protective film covering the surface of a plant leaf.

Gall

An abnormal outgrowth of tissue in plants designed to limit the spread of an invading pathogen.

Trichomes

Small hairs on the surface of plants used to deter pathogens and/or insects.

Stoma

A small pore on the leaf's surface that opens and closes to regulate gas exchange.

Microbiota barrier

A component of the first line of defence in which the presence of normal flora limits the growth of pathogenic bacteria.

Cilium

Thin, hair-like projection that protrudes from eukaryotic cells.

Flora

Naturally occurring, non-pathogenic bacteria present in an organism.