LECTURE 2
INFECTION IMMUNITY AND PROTECTION
IMMUNE RESPONSES TO BACTERIAL PATHOGENS
Normal flora of humans inhabit:
Nose and nasal pharynx (Staphylococci).
Oropharynx (Streptococci).
Mouth (Actinomyces, yeast).
Skin (Staphylococci, Streptococci, diptheroids).
Gastro-intestinal tract (small and large intestine).
Genito-urinary tract (kidneys, bladder, vagina and cervix).
IMMUNE SYSTEM IN HEALTH AND DISEASE
Infectious diseases – the result of a less effective human immune
system
Infection verses disease
Latent infections and carrier state – source of infection to other
individuals
Knowledge of immune response and pathogen evasive strategies
- important for developing preventive and therapeutic measures
IMMUNE RESPONSE TO INFECTIOUS DISEASES
A pathogen establishes an infection in a susceptible host when both innate
and adaptive host defenses are circumvented.
Innate immunity and pathogen recognition
Innate immunity forms the 1st and 2nd line defense against pathogens.
Innate immunity recognizes the invading pathogens.
Recognition is through pattern recognition receptors (PRRs).
PRRs are located on cells of innate immune system i.e. macrophages,
33
, Pattern recognition receptors (PRR) are a class of innate immune
response proteins that respond to invasion of host tissue by
foreign particles and tissue destruction signals.
Foreign particles or pathogens are recognized by their pathogen-
associated molecular patterns (PAMPs).
Tissue destruction signals e.g. endogenous stress signals are
recognized as danger-associated molecular patterns (DAMPs).
Pathogen-associated molecular patterns (pamps)
They are small molecular sequences or patterns that are highly
conserved and consistently found on pathogens. These molecular
patterns are recognized by Pattern recognition receptors (PRRs)
of innate immune cells.
Some examples of PAMPs include:
●Bacterial lipopolysaccharide or toxins e.g. LPS found on gram –
ve bacteria
●Bacterial flagellin
●Bacterial lipoteichoic acid
●Bacterial lipoproteins and peptidoglycan (PDG)
●Mannose residues and N-formylmethionine,
●Fungal glucans,
●Viral nucleic acids associated with viruses ssRNA, ds RNA, DNA
●Bacterial DNA and unmethylated cytosin-guanosin dinucleotide
(CpG)
Residues
Damage associated molecular patterns (damps)
They are endogenous danger signal molecules produced in response to
tissue damage (inflammation), cell death and activation of antigen
presenting cells (APCs) and lymphocytes.
They may function as primal initiators or simply give positive-feedback to
enhance or modify an ongoing response.
34
INFECTION IMMUNITY AND PROTECTION
IMMUNE RESPONSES TO BACTERIAL PATHOGENS
Normal flora of humans inhabit:
Nose and nasal pharynx (Staphylococci).
Oropharynx (Streptococci).
Mouth (Actinomyces, yeast).
Skin (Staphylococci, Streptococci, diptheroids).
Gastro-intestinal tract (small and large intestine).
Genito-urinary tract (kidneys, bladder, vagina and cervix).
IMMUNE SYSTEM IN HEALTH AND DISEASE
Infectious diseases – the result of a less effective human immune
system
Infection verses disease
Latent infections and carrier state – source of infection to other
individuals
Knowledge of immune response and pathogen evasive strategies
- important for developing preventive and therapeutic measures
IMMUNE RESPONSE TO INFECTIOUS DISEASES
A pathogen establishes an infection in a susceptible host when both innate
and adaptive host defenses are circumvented.
Innate immunity and pathogen recognition
Innate immunity forms the 1st and 2nd line defense against pathogens.
Innate immunity recognizes the invading pathogens.
Recognition is through pattern recognition receptors (PRRs).
PRRs are located on cells of innate immune system i.e. macrophages,
33
, Pattern recognition receptors (PRR) are a class of innate immune
response proteins that respond to invasion of host tissue by
foreign particles and tissue destruction signals.
Foreign particles or pathogens are recognized by their pathogen-
associated molecular patterns (PAMPs).
Tissue destruction signals e.g. endogenous stress signals are
recognized as danger-associated molecular patterns (DAMPs).
Pathogen-associated molecular patterns (pamps)
They are small molecular sequences or patterns that are highly
conserved and consistently found on pathogens. These molecular
patterns are recognized by Pattern recognition receptors (PRRs)
of innate immune cells.
Some examples of PAMPs include:
●Bacterial lipopolysaccharide or toxins e.g. LPS found on gram –
ve bacteria
●Bacterial flagellin
●Bacterial lipoteichoic acid
●Bacterial lipoproteins and peptidoglycan (PDG)
●Mannose residues and N-formylmethionine,
●Fungal glucans,
●Viral nucleic acids associated with viruses ssRNA, ds RNA, DNA
●Bacterial DNA and unmethylated cytosin-guanosin dinucleotide
(CpG)
Residues
Damage associated molecular patterns (damps)
They are endogenous danger signal molecules produced in response to
tissue damage (inflammation), cell death and activation of antigen
presenting cells (APCs) and lymphocytes.
They may function as primal initiators or simply give positive-feedback to
enhance or modify an ongoing response.
34
