Immunology Quiz on Immune System Effects

Immunocompromised Host

• Lecture 25
• Objectives include reviewing the basics of innate and adaptive immune systems and providing an overview of immune system deficiencies that lead to infectious diseases.
• Classic features of inflammation include rubor (redness), calor (heat), tumor (swelling), and dolor (pain).
• A patient's immune status (e.g., immunodeficiencies, past infections, vaccination) significantly impacts their clinical presentation.
• Examples include a post-kidney transplant patient with Pseudomonas aeruginosa in their urine, a healthy 30-year-old non-smoker with non-resolving pneumonia despite antibiotics, a 16-month-old with frequent pneumonia, and a 56-year-old man bitten by a dog with past lymphoma.

Innate and Adaptive Immunity

• Innate immunity involves non-specific defenses, a fast response, and a lack of memory.
  • It includes fever, dendritic cells, NK cells, macrophages, epithelial cells, and the complement system.
• Adaptive immunity involves a trained immune system, a slower response, and a memory component.
  • It includes B cells, plasma cells, antibodies, T helper cells, and T killer cells.
  • The difference in these attributes impacts the duration and severity of infections.

Innate Immunity - Barriers and Secretions

• Skin has many cell layers, tightly packed cells, and dead outer layers with live inner layers.
• Mucous membranes have one to a few layers of cells, moist environment, cells mostly alive, mucous present.
• Digestive system secretions (saliva, stomach acid, gastroferritin, bile, intestinal secretions) wash microbes or digest them, preventing microbial use of iron, and eliminating microorganisms using peristalsis, defecation, and vomiting.
• Urinary system secretions (urine) eliminate microorganisms via acidity and flushing.
• Reproductive system secretions (vaginal, menstrual flow, prostate secretions) inhibit microbes and wash them from the tract.
• Cardiovascular system blood flow removes microorganisms from wounds and coagulation prevents pathogen entry.

Innate Immunity - Cells

• Macrophages ("big eaters") are phagocytes that engulf and destroy microbes.

Adaptive Immunity - Overview

• Antibody-mediated (humoral) immunity involves B cells and plasma cells producing antibodies to neutralize or eliminate pathogens.
• Cell-mediated immunity involves T helper and T killer cells directly destroying infected or malignant cells.

Immunodeficiency States

• Primary immunodeficiencies are genetic disorders causing immune system deficiencies, such as Chronic Granulomatous Disease, Severe Combined Immunodeficiency (SCID), DiGeorge syndrome, and Bruton-type agammaglobulinemia.
• Secondary (acquired) immunodeficiencies are caused by infections, splenectomies, malignancies, chemotherapy, steroids, transplant rejection drugs, poor nutrition, pregnancy, and the newborn period.

Secondary Acquired Immunodeficiencies

• Chemotherapy interferes with lymphocyte replication, often leading to temporary neutropenia and increased infection risk.
• Corticosteroids damp down inflammation, potentially impairing PMN migration to infection sites and reducing macrophage/dendritic cell function, resulting in increased susceptibility to various infections.

Secondary Acquired Immunodeficiencies (continued)

• Post-transplant immunosuppressants like cyclosporine, tacrolimus, and serolimus inhibit cytokine production and T cell function, increasing infection risk.
• Splenectomy removal of the spleen reduces the production of opsonizing antibodies, leading to higher risks of infections by encapsulated bacteria (like Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis).
• HIV/AIDS is characterized by a progressive decline in CD4+ T cells, increasing susceptibility to opportunistic infections.

Evasion of the Immune Response

• Bacteria can evade the immune response by destroying complement components, destroying immunoglobulins (e.g., producing IgA protease), preventing phagocytosis (e.g., encapsulating), and preventing intracellular killing.
• Some bacteria change surface antigens rapidly, evading the immune system's targeted response.

Important Topics Beyond Scope

• Dysregulation, autoimmunity, and allergy are important parts of the immune system but beyond the scope of this lecture.

This quiz explores key concepts related to the immune system, focusing on the effects of corticosteroids, the risks associated with immunosuppressive agents, and the impact of splenectomy. Test your knowledge on immune response, inflammation, and immunodeficiencies in a range of scenarios.