Immune stimulation Sometimes antibodies elicited by normal flora cross-react with normal tissue Antibodies against ABo blood group substances .A- make b antibodies ·B- make a antibodies .0-make antibodies against both Why? Bacteria from intestinal flora contain Ag that cross-react with both a &b blood substances BIOL 533 7 Lecture two
BIOL 533 7 Lecture Two Immune Stimulation • Sometimes antibodies elicited by normal flora cross-react with normal tissue: – Antibodies against ABO blood group substances: • A - make B antibodies • B - make A antibodies • O - make antibodies against both – Why? Bacteria from intestinal flora contain Ag that cross-react with both A & B blood substances
Immune stimulation Cross-reactivity does not normally cause disease Possible for antibodies cross-reactive to microbial Ag to cause problem Lupus erythematosus-production of Ab against host dna Some evidence that ag may be cross-reacting bacterial LPS May cross-react with pathogen(meningococcus) BIOL 533 Lecture two
BIOL 533 8 Lecture Two Immune Stimulation • Cross-reactivity does not normally cause disease – Possible for antibodies cross-reactive to microbial Ag to cause problem • Lupus erythematosus—production of Ab against host DNA – Some evidence that Ag may be cross-reacting bacterial LPS • May cross-react with pathogen (meningococcus)
Phyl& hemical Aspects带 Keeps out invaders Mechanisms Physical advantage of previous occupancy Some produce bacteriocins or antibiotics Relevance to lab work e coli K-12 cannot compete with intestinal flora BIOL 533 Lecture two
BIOL 533 9 Lecture Two Physical & Chemical Aspects • Keeps out invaders – Mechanisms: • Physical advantage of previous occupancy • Some produce bacteriocins or antibiotics – Relevance to lab work: E. coli K-12 cannot compete with intestinal flora
Phyl& hemical Aspects带 Antibiotic effects: wipes out normal flora Both endogenous and exogenous organisms can cause disease Infecting dose of Salmonella decreases one million-fold when mice given streptomycin Patients treated with some potent antibiotics Suffer from diarrhea due to overgrowth of yeasts and staphylococci Administration of clindmycin -Clostridium difficile(minor member of normal flora) causes pseudomembranous colitis BIOL 533 Lecture two
BIOL 533 10 Lecture Two Physical & Chemical Aspects • Antibiotic effects: wipes out normal flora – Both endogenous and exogenous organisms can cause disease • Infecting dose of Salmonella decreases one million-fold when mice given streptomycin • Patients treated with some potent antibiotics: – Suffer from diarrhea due to overgrowth of yeasts, and staphylococci – Administration of clindmycin-Clostridium difficile (minor member of normal flora) causes pseudomembranous colitis
Phyl& hemical Aspects带 Role in human nutrition and metabolism E, coli and bacteriodes synthesize vitamin K Metabolism of key compounds involves excretion from liver into intestine and their return to the liver BIOL 533 Lecture two
BIOL 533 11 Lecture Two Physical & Chemical Aspects • Role in human nutrition and metabolism – E. coli and Bacteriodes synthesize vitamin K – Metabolism of key compounds involves excretion from liver into intestine and their return to the liver