Strep Throat

By Mark Kresevic bacterial infection


Streptococcus pyogenes is one of the most frequent pathogens of humans. It is estimated that between 5-15% of normal individuals harbor the bacterium, usually in the respiratory tract, without signs of disease as seen in the picture to the right.


Group A Streptococcus prudces pilus like structures containg rtective antigens and lancefielf T antigens

Streptomycin is a screening test used to detect antibodies to several streptococcal antigens. An antigen is a substance that can trigger animmune response, resulting in production of an antibody as part of the body's defense against infection and disease.


Whenever we have an infection our body's immune system ramps up to fight off the infection. One of the ways it does this is to produce "antibodies" that are specifically programmed to kill the invading bacterium. This is exactly how our immune system fights off a Streptococcus pyogenes infection. Our immune system usually wins this battle, successfully killing off the invading Streptococcus pyogenes bacteria present in our body

Immune Response

A foreign substance that invades the body is called an antigen. When an antigen is detected, several types of cells work together to recognize and respond to it. These cells trigger the B lymphocytes to produce antibodies.Once the B lymphocytes have produced antibodies, these antibodies continue to exist in a person’s body. If the same antigen is presented to the immune system again, the antibodies are already there to do their job. This principle forms the basis of immunizations. The immunization introduces the body to the antigen in a way that does not make a person sick, but it does allow the body to produce antibodies that will then protect that person from future attack. The T cells are part of the system that destroys antigens that have been tagged by antibodies or cells that have been infected or somehow changed. T cells are also involved in helping signal other cells of the immune system to do their jobs.


Though the bacterium itself has such a wide range of virulence factors that make it

difficult for the immune system to destroy, the immune system is aided in large part by

medications and antibiotics which make the job much easier. When the immune system identifies foreign matter or material in the body, different defense mechanisms, such as

phagocytes, are activated to seek out and destroy or neutralize those foreign substances.

Such is the case with S. pyogenes. Strep throat is well adapted in that it has features

which obstruct the work of the phagocytes . Fortunately, phagocytes are not the only

features and adaptations of the immune system and with antibiotics, (which usually are

affective against S. pyogenes) people recover.

Line of Defense

The lysozyme. 1st Line of Defense 2nd Line of Defense 3rd Line of Defense Goal Phagocytic cells known as macrophages ingest the pathogen. The macrophage then becomes the Antigen Presenting cell, which means it shows the strep throat antigen, which in turn activates the third line of defense. acquired or specific immune responses: When the antigen is all killed and then remembered the antibodies, The strep bacteria is beaten off and your throat is safe, for now. Phagocytes attack! some of the pathogens entered your mouth from your significant other's. As the strep throat pathogen enters the mouth, it manages to get by the first line of defense, which is the enzyme lysozyme contained in saliva. When the antigen is presented, a helper T cell recognizes the danger present. It quickly spreads the word to the B cells, which then clone and specialize the antigen into plasma cells to produce antibodies. As soon as this occurs, the killer T cells, come and completely kill off the antigen. The regulatory T cell signals the killer T to stop, and the memory T/B cells takes a small portion of the antigen to remember it by, so it can activate the antibodies the next time the strep pathogen is present.