Chapter 17

Innate Immunity

• present from birth

• targets any foreign invader

• immediate

• non-specific

Adaptive Immunity

• develops after exposure to pathogens

• highly specific to particular antigens

• slower

• specific/aquired

1st Line of Defense

• nonspecific

• physical & chemical barriers

• prevents entry of pathogens

2nd Line of Defense

• nonspecific

• phagocytes, inflammation, fever, antimicrobial substance

• destroys invaders that breach barriers

3rd Line of Defense 

• specific

• lymphocytes (B&T cells), antibodies 

• targets specific antigens, forms memory

Physical Defenses

• skin

• mucous membranes

• tears, saliva, urine flow

• normal microbiota

Chemical Defenses

• sebum

• lysozyme

• sweat

• acidic pH of skin

• gastric juice in stomach (HCI acid)

• Digestive enzymes and bile

• semen

• vaginal secretions

• antimicrobial peptides

• plasma proteins mediators

Hematopoietic

production of blood cells; in bone marrow

Neutrophils

• nucleus lobes, pale lilac granules

• react early, phagocytic, effective against bacteria

• most common leukocyte

• Granulocytes

Eosinophils

• two lobed; red-orange granules

• phagocytic cells(parasitic worms); antigen-antibody complexes, parasitic infections, allergic responses

• Granulocytes

Basophils

• nucleus two-lobed, heavy dense dark purple granules

• pro-inflammatory; releases histamine

• least common leukocyte

• Granulocytes

Lymphocytes

• large nucleus, purple

• primarily specific (adaptive) immunity, natural killer cells, non-specific

• Agranulocytes

Monocytes

• Largest leukocyte; indented or horseshoe-shaped nucleus

• very effective phagocytic cells; antigen-presenting cells (APCs)

• referred to as macrophages and dendritic cells after leaving the circulation

• Agranulocytes

Diapedesis

migration of cells out of blood vessels into the tissues (squeeze their way thru)

Chemotaxis

migration in response to specific chemicals at the site of injury or infection (attracted to chemical)

Pathogen-associated molecular patterns (PAMPs)

• recognized by PRRs

• a “badge” shared by an entire class of pathogen

Pattern recognition receptors (PRRs)

• not specific to a single-cell type

  • e.g. tool-like receptors (TLRs)

Inflammatory Response

redness, warmth, swelling, pain & loss of function

Fever

initiated by circulating pyrogens

Exogenous pyrogens

products of infectious agents

Endogenous pyrogens

released by leukocytes

Benefits of a Fever

• inhibits microbial growth

• speeds up immune system’s reaction

• helps body heal faster

Phagocytosis

1) chemotaxis

2) Adherence

3) Ingestion

4) Digestion

5) Killing

Interferons

• small proteins produced by certain WBCs & tissue cells

• produced in response to viruses, etc.

• signals neighboring uninfected 

Complement System

• second line; non-specific

• cascade reaction (domino effect)

• complement proteins