Five infectious agents
- bacteria
- viruses
- Fungi
- Parasites
- Prions
Bacteria
single cell organisms that can independently reproduce and need a host to supply food
- cause common infections and killed by antibiotics
Exotoxins
proteins secreted and released by bacterial cell during growth
Endotoxins
trigger inflammatory process end produce fever
Septicemia (sepsis)
systemic spread of toxins through bloodstream
Viruses
- cause most infections
- much smaller than bacteria
- cannot grow without another organism
- incapable of metabolism
- can only treat symptoms, no cure
Fungi
- yeasts/mold
- more like plants than animals
Mycoses
fungus infections
Parasites
- protozoa to large intestinal worms
- treatment depends on organism and location
Prions
- differ from viruses, smaller
- made entirely from proteins
- do not have protective capsids
Three lines of defense
- anatomic barriers
- inflammatory response
- immune response
Anatomic barriers
protect from external and nonspecific things
Inflammatory barriers
protect from internal and nonspecific things
Immune response
protect from internal and specific things
Immunity
long term protection against specific foreign substances
Natural immunity
born with, part of genetic makeup
Acquired immunity
develops as outcome of immune response
Active acquired immunity
generated by hosts immune system after exposure to antigen
- long lasting
Passive acquired immunity
transferred to person from outside source
- temporary
Immunoglobulins
antibodies
Primary immune response (initial)
first exposure to antigen
Secondary immune response (anamnestic)
second exposure
Lymphocytes
responsible for recognizing foreign antigens, producing antibodies, and developing memory
B lymphocytes
do not attack antigens direcly
Humoral immunity
long term immunity to specific antigens
T lymphocytes
do not produce antibodies
Cell-mediated immunity
recognize presence of foreign antigen and attacks it directly
Immunogens
antigens that trigger immune response
HLA antigens
body recognizes as self or foreign
Universal recipient
Blood type AB
ABO blood groups
two types of antigens present on surface of RBC's, A and B
Universal donor
Blood type O
Direct effect of antibodies on antigen
- agglutination
- precipitation
- neutralization
Indirect effect of antibodies on antigen
- enhancement of phagocytosis
- activation of plasma proteins
Four main functions of antibodies
- neutralization of bacterial toxins
- neutralization of viruses
- opsonization of bacteria
- activation of inflammatory processes
IgM
largest immunoglobulin
IgG
memory"
- recognizes repeated invasions of antigen
IgA
present in mucous membranes
IgE
least concentrated immunoglobulin
IgD
very low concentrations
Isotypic antigens
species specific
Allotypic antigens
can differ within the same individual
Idiotypic antigenic
can differ within same individual
Monoclonal antibody
produced in labratory, pure and specific to single antigen
Secretory immune system
lymphoid tissues beneath mucosal endothelium
- protects body from pathogens inhaled or ingested
T cells
- do not produce antibodies
- attack pathogens directly and create temporary immunity
- travel through thymus gland
Memory cells
secondary immune responses
Td cells
transfer delayed hypersensitivity
Tc cells
cytotoxic
Th cells
helper cells
- interact with both Tc cells and B cells
Ts cells
suppressor cells
Cytokines
proteins produced by white blood cells, they are the messengers of immune system
Monokine
cytokine released by macrophage
Lymphokine
cytokine released by lymphocyte ( T or B cell)