Immune Evasion, Subversion, and Hypersensitivity Types in Pathology

What is genetic variation of pathogens?

Different strains of pathogens have different epitopes due to mutation and recombination.

What is antigenic drift?

Small mutations in pathogens that lead to changes in their antigens.

What is antigenic shift?

A significant change in the pathogen that results in a new type.

What is adaptive evasion in pathogens?

Gene arrangement that allows pathogens to change their surface antigens to evade the immune system.

Give an example of a pathogen that uses adaptive evasion.

Campylobacter fetus subspecies venerealis, which changes its surface coat to prevent immune elimination.

How do some bacteria evade the immune system?

By secreting proteases that destroy immunoglobulins or cytokines.

How have pathogenic mycobacteria evolved in relation to host macrophages?

They have evolved to survive within host macrophages, as seen in Johne's disease.

What is subversion in the context of pathogens?

The ability of pathogens to hide from the immune response, often going silent until the immune response subsides.

Provide an example of a pathogen that can go latent.

Herpes simplex virus.

What are under-reactions in immune responses?

Immune responses that are insufficient to combat pathogens, such as in Bovine Viral Diarrhea (BVD).

What are over-reactions in immune responses?

Exaggerated immune responses that can lead to tissue damage or autoimmune diseases.

What is antibody deficiency?

An inability to clear extracellular bacteria due to problems in the immune system's B cells progressing to plasma cells.

What leads to Acquired Immune Deficiency Syndrome (AIDS)?

When a pathogen can escape the immune system and the host has an immune deficiency.

What is an autoimmune disease?

A disease caused by adaptive immunity responses that misdirect to attack healthy tissue.

What is a characteristic of Type I hypersensitivity?

Allergic reactions mediated by IgE antibodies and an exaggerated T helper cell response.

What occurs in Type II hypersensitivity?

The immune response destroys normal cells, often due to sensitization to another blood type.

What defines Type III hypersensitivity?

The formation of immune complexes from antigens and antibodies, leading to severe inflammation.

What is Type IV hypersensitivity?

A delayed hypersensitivity mediated by T and NK cells, resulting in a slow inflammatory response.

What is Type V hypersensitivity?

An abnormal immune response against substances and tissues normally present in the body, leading to autoantibody production.