7A Pathogens and Antigens

What is a pathogen

An agent/microorganism that causes disease

Types of pathogens

Cellular or Non cellular

What is non-cellular pathogens

Non-cellular pathogens do not have a cellular structure and are non-living.

What is Cellular Pathogens

Cellular pathogens have a cellular structure and are living organisms.

Cellular Pathogens

B - Bacteria

E - Endoparasite

E - Ectoparasite

P - Protozoa

Y - Yeast/Fungi

Non-cellular pathogens

Viruses

Prions

Bacteria

Unicellular prokaryotes that can infect any part of body and cause diseases through production of toxins and enzymes that affect or kill cells.

Example of Bacteria

E. coli, salmonella

Unicellular Protozoa

Single celled eukaryotic organism. Reproduce through sexual or asexual reproduction

Fungi/Yeast

Eukaryotic organisms that infect exterior of host.

Multicellular ECTOparasites

Attach externally to host

lice, ticks, mites

Multicellular ENDOparasites

Internal infection - worms

Viruses

Noncellular, can only replicate inside a cell and infect all cellular organisms. Must insert genetics into host to reproduce and form new virus which can leave and infect other host cells.

Structure of a viruses

Basic structure of protein coat (capsid) enclosing genetic material (DNA/RNA)

Example of Viruses

HIV, Covid-19, Rabies, Polio, Measles

Prions

infectious/misfolded protein particles that do not have a genome. Cause normal proteins to convert which affects nervous system, transmissible and no cure

What are toxins

Various poisonous substances produced/within by some microorganisms

What are antigens

The immune system uses antigens to recognize if a cell or molecule is self or non-self. If it is identified as non-self, an immune response is initiated

Antibody vs Antigen

antibody is found in your body while antigen is found on the pathogen.

Self Antigens

Self-antigens, which are located on the surface of cells, mark the cells of an organism as 'self' so that the immune system doesn't attack them. Two types of markers

MHC Class I markers

are expressed on all nucleated cells in the body. all cells in the human body except for those without a nucleus (e.g. red blood cells) express MHC Class I markers.

MHC Class II markers

are found on specialized cells of the immune system

Non-Self Antigens

Seen as 'foreign' or not belonging to that individual. If a non-self antigen is recognized within the body, the immune system is activated and attempts to eliminate it.

Examples of Non-self Antigen

Organ Transport - always recognized as non-self therefore IMS suppression drugs must be taken. Or genetic similarity reduces Non-self

Allegens

harmless substances that trigger allergic reactions in the body

symptoms: swelling, itching, mucus production

How is the immune system able to recognize self-cells and non-self cells and why is this important

Detect self antigens displayed by self cells which allows it to distinguish from non-self cells which display non-self antigens.

The presence of non-self antigens can stimulate an immune response to protect the body from disease. It also ensures that the immune response is not directed towards self cells or it will cause harm to the organism - autoimmune disease