Immune System

Innate Immunity

• Non-specific defense system
• Response is immediate
• has been found in vertebrates and invertebrates, along with plants
• innate immunity recognizes pathogens by detecting molecules that are common in pathogens, but not in the body.
• there are two types of innate immune responses: inflammatory/phagocytosis

Innate Defenses

• skin and mucus - prevents entry of microorganisms
• antimicrobial proteins, phagocytes, and other cells - inhibit spread of invaders and inflammation is its most important mechanism
• surface barriers - keratin and epithelial membranes

Innate Defenses Continued

• Epithelial membranes produce protective chemicals to destroy microorganisms, protect through:
• skin acidity
• sebum contains toxic chemicals
• stomach mucosa secretes concentrated HCl and protein digesting enzymes
• saliva and lacrimal fluid have lysozyme
• mucus traps in the digestive/respiratory

Innate Defenses Continued

• phagocytes and natural killer cell: macrophages, neutrophils, eosinophils, mast cells, and Nk cells
• Macrophages are chief phagocytes
• Neutrophils become phagocytes when encounter w/ infectious material
• eosinophils fight parasites
• mast cells bind and ingest bacteria
• natural killers react nonspecifically

1st Line of Defense

2nd Line of Defense

2nd Line of Defense

Adaptive Immunity

• Typically begins with antibodies created by B lymphocytes
• Parts in acquired immunity include:
• Dendritic cells
• Cytokines

Building Immunity

• Not present at birth
• Response to antigen is permanent once developed by immune system
• White blood cells responsible for Adaptive immunity

T Lymphocyte: responsible for building responses to antigens

B Lymphocyte: WBC responsible for building responses to antigens

B Lymphocytes

• Work to make antibodies to the infection while T cells fight the infection
• Not thymus-dependent
• Have a short lifespan
• Are responsible for production of immunoglobulins
• Mature in the bone marrow
• Can mature into two different types: plasma B cells and memory B cells

Plasma B Cells

• Produce and secrete antibodies to fight off infection
• All plasma cells descended from a single B cell produce the same antibody directed toward the antigen that stimulated it to mature

Memory B Cells

• Have an affinity for a particular antigen
• "Remember" the stimulus that led to their formation

Antibodies and B Cells

• Attach to a specific antigen
• Membrane bound
• Released into the blood stream proteins that know to fight off a specific infection

T Lymphocytes

T lymphocytes

• Produced in bone marrow but migrate to the thymus gland to mature as needed
• They are released into the bloodstream by the immune system to perform as mediators of cellular immunity

Untitled Slide

• T lymphocytes participate in hypersensitivity reactions, reactions to allergens or toxic substances, graft-versus-host reactions, etc.

Types of T lymphocytes

• The immune system sends helper T cells (CD4+ T cells) when it detects specific types of antigens on the surface of non-self-cells that have invaded the body.
• Killer T cells (CD8+ cells) are activated to attack specific tumor cells and certain viruses and parasites whose surface antigens they recognize

Untitled Slide

• Regulatory T cells perform a slightly different function, protecting against self-cells that mistakenly attack certain body tissues in autoimmune disease.

Role in Disease

• Having detaching the invader by its shape, it sends either the killer T cells or helper T cells to attack.
• Helper T cells release cytokines to the rest of the immune system. So your body produces "weapons" to fight bacteria, viruses or parasites that have entered.
• Killer T cells will kill virus-infected cells directly.