Immunology MSK Flashcards
What is Osteomyelitis, and what is the biggest general cause?
Inflammation of the bone usually due to infection
What are the risk factors for getting Ostesomyelitis?
Diabetes
Kidney Failure
Smoking, IV drug use
Traumatic wounds, joint replacement
What are the biggest specific causes of Osteomyelitis
Staphylococcus Aureus
TB —Pott Disease
Also: Salmonella (sickle cell), staph epidermidis (prosthetics), Pasteurella multocida, Gonorrhea
What are the characteristics of Staph Aureous?
What is the species characterized by?
Grape cluster look
Gram Positive
Aerobic
Catalase positive
B-hemolytic
(Common places: Nares, ears, axilla, groin.)
Coagulase (other staph don’t produce it)
—Coagulase helps to convert fibrinogen to fibrin resulting in a clot****
Protein A— binds host antibodies to prevent antibody-mediated clearance of the bacteria.
Polysaccharide A
Why is Staph Aureus such a good pathogen?
Virulence Factors!!!
- Structural components, toxins, enzymes.
What are the virulence factors of Staph Aureus
Capsule: inhibits chemotaxis and phagocytosis
Slime Layer: facilitates adherence to foreign bodies. BIOFILM FORMATION
Peptidoglycan: provides osmotic stability, stimulates production of endogenous pyrogen and inhibits phagocytosis.
Teichoic acid: binds to fibronectin
Protein A: inhibits antibody-mediated clearance by binding IgG1, 2, and 4
What do these virulence factors of staph aureous do?
Coagulase
Hyaluronidase
Fibrinolysin
Lipases
Nucleases
Coagulase: Converts fibrinogen to fibrin
Hyaluronidase: hydrolyzes hyaluronic acids in connective tissue, promoting spread of staphylococci in tissue
Fibrinolysin: Dissolves fibrin clots
Lipases: Hydrolyze lipids
Nucleases: Hydrolyze DNA
What are the toxins of Staph Aureus?
Cytotoxic
Exfoliative toxins: scalded skin syndrome
Enterotoxins: Food poisoning
Toxic Shock Syndrome Toxin: TSST
Superantigens
From Pericarditis, Myocarditis, and Endocarditis, which one is caused most by Staph Aureus?
Endocarditis
It is the layer in contact with the blood.
What is infective Myositis?
Relatively rare acute infection of skeletal muscle
Usual suspect: S. Aureous
What are some causes of Viral Arthrities?
Hepatitis B: prodromal period before diagnosis
Rubella, Mumps, Ross River, Parvovirus
What is one of the main causes of Myonecrosis Gangrene?
What is the pathogenesis?
Clostridium perfringens: from Fecal contaminant
They are anaerobic
Pathogenesis
- Multiply subcutaneously
- Anaerobic cellulitis
- Invasion of muscle
- Gas production, necrosis
- If toxin escapes into blood, leads rapidly to death by hemolysis, or renal failure.
Explain Clostirdium Perfringens
Gram positive rod, spore forming anaerobes.
Hyperbaric chamber therapy might be helpful.
Toxins cause clumping of leukocytes in blood vessels so the immune system cannot get to the site.
2 kinds of toxins:
Perfringolysin O— Pore forming
Alpha Toxin— Lecithinase or phospholipase C
-Destroys Cell Membranes (Antitoxin not effective)
Describe Systemic Autoimmuniteis
General defect in immune regulation (hyperactive T and B cells)
Presence of antinuclear antibodies (anti-dsDNA and anti Sm antibodies)
Tissue damage of both CMI and humoral responses.
Autoantibodies causing direct cellular damage: Type ll Hypersensitivity Deposition of immune complexes: Type lll Hypersensitivity T cell mediated damage: Type lV Hypersensitivity
Lupus
SLE (systemic lupus erythematosus). Breakdown of tolerance to self antigens.
Can be a genetic or environmental effect
(C1q, C2, C4, HLA-D2, MBL)
(UV light, gender, infection)
Defective clearance of apoptotic bodies leads to an increased burden of nuclear antigens.
Results in generation of anti-nuclear antibodies (ANAs)
