Lecture 9

Immune system

Network of different organs, cells, and tissues that protect the body from pathogens.

Pathogens

Consist of viruses, protozoa, parasite, bacteria, and fungi.

Order of smallest to largest pathogens

Virus, intracellular bacteria, extracellular bacteria + protozoa, fungi, parasites.

Extracellular pathogens

Streptococcus pneumonia – gram-negative bacteria – causes pneumonia.

Serotypes

There are more than 90 different serotypes for Streptococcus pneumonia, meaning we need 90 different antibodies.

Clostridium tetani

Causes tetanus via the release of tetanospasmin.

Tetanospasmin

A typical dose of tetanospasmin is too small to provoke an immune response.

Influenza

A type of intracellular pathogen. Viruses are always intracellular and therefore look a little like human cells, which makes them difficult to attack by the immune system.

Adaptive immune system

Has to respond to mutated pathogens.

HIV

Contains yellow spike proteins which allow it to dock and enter the body. Inside the matrix is the capsid, where there are 2 copies of RNA which has reverse transcriptase which allows copies of RNA and DNA to be made and duplicated in our cells.

Antigenic drift rate

So rapid that it outpaces the development of an effective immune response, making it difficult to develop a vaccine for it.

Antigenic shift/variation

Another challenge faced by the immune system. Initial infection develops a response to get rid of the pathogen. However, if the pathogen alters its surface proteins, the immune response can be avoided.

Plasmodium falciparum

When a person is bitten by Plasmodium falciparum, the gametocytes in blood are transferred to a mosquito vector. The gametocytes hatch out into gametes and zygotes and affect its gut, becoming sporozoites in the salivary gland. Now when it bites another person, the sporozoites enter another person and replicate in the liver and grow in the liver until they rupture the red blood cell and release gametocyte in humans.

Adaptive immune response

Involved in the generation of antibodies to clear away pathogens. It can take a week to gather antibodies to destroy pathogens. However, a second exposure only takes 4 to 6 days to gather antibodies. It is faster and bigger.

Innate immune response

Starts early on and relies on barriers and chemical warfare and makes calls for help.

Humoral arm

Relies on barriers and chemical warfare and makes calls for help.

Cell-mediated arm

Comprises a range of phagocytic cells and natural killer cells that destroy virus-infected cells. All these respond to calls for help from the innate humoral arm.

Tissue-specific response

Different tissues display different immune responses.

Too much use of immune response

Can damage the host.