HUBS191 Lecture 37: Insufficient or Overactive Immune Response

Immune Deficiencies

• Can be inborn or induced by viruses, medical treatments, or poor nutrition.

Severe Combined Immunodeficiency (SCID)

• X-chromosome linked, more common in XY-males.
• Patients lack functional T and B cells.

Virus-Induced Immune Suppression

• Measles, HIV, and other viruses interfere with the host's immune system.
• HIV targets and kills CD4 T cells, diminishing help for antibody and cytotoxic responses.

Human Immunodeficiency Virus (HIV)

• HIV receptor is the CD4 molecule on CD4 T cells.
• Infection leads to the loss of CD4 T cells.
• Impacts immunity to microbes and cancer.

Autoimmune Disease

• Normally prevented by immune tolerance mechanisms.
• Adaptive immune response mediates autoimmune attacks.

Immune Tolerance

• Critical to avoid autoimmunity.
• Thymus deletes autoreactive T cells.
• Failures can lead to autoimmunity.

Rheumatoid Arthritis (RA)

• Autoimmune disorder affecting joints.
• Autoreactive T and B cells attack self-antigens in joints.
• Affects ~1% of the population, often with late onset.

Diabetes Type 1

• Insulin beta-cells are attacked.

Allergic Reactions

• Allergens are harmless environmental antigens.
• Outcomes range from hay fever to systemic anaphylaxis.

Allergic Reactions: Effector Response

• Dendritic cells present allergen peptides to helper T cells.
• Helper T cells activate B cells to secrete IgE.
• IgE binds to mast cell receptors (FcR).
• Allergen binding to FcR on mast cells triggers degranulation and histamine release.

Peanut Allergies

• Most common cause of food allergies in children.
• Leading cause of anaphylaxis and death related to food allergy in the U.S.

Fc Receptors (FcR)

• Bind to the Fc domain of antibodies, facilitating phagocytosis and mast cell activation.