Humoral Response 2 Flashcards
Neutralization: Fab
- virus binds to cell surface
- receptor mediated endocytosis of virus
- acidification of endoscope after endocytosis triggers fusion of virus with cell and entry of viral DNA
- antibody blocks binding to virus receptor and can also block fusion event
Opsonization: Fab and Fc
Antibody opsonization is a process by which a pathogen is marked for destruction by:
▪ antibody-dependent cellular phagocytosis (ADCP)
▪ antibody-dependent cellular cytotoxicity (ADCC)
What is the function of FcyRI
Phagocytosis and activation of phagocytes
Found on macrophages ,neutrophils ,eosinophils
ADCP: Fab/Fc
Antibodies of certain IgG subclasses bind to microbes and are recognized by Fc receptors on phagocytes
-signals promote phagocytosis
ADCC (NK cells): Fab/Fc
Antibodies of IgG1 and IgG3 binds to cells and their Fc regions are recognized by an Fcy receptor on NK cells
The NK cells are activated and kill the antibody -coated cells
ADCC (eosinophils): Fab/Fc on IgE
- FceRI
- IgE antibody binds to helminths and recruits and activates eosinophils via FceRI leading to degranulation of the cells and release toxic mediators
- IL5 secreted
Transported across the epithelium
IgA
Transported across the placenta
IgG1
▪ Antibodies also serve protective functions in 2 special sites
- mucosal organs
* Fetus/neonate gut
Mucosal immunity
Immunoglobulin A is produced in mucosal lymphoid tissues
▪ Transported across epithelia
▪ Neutralizes microbes in lumen of mucosal organs
Neonatal Immunity
Passive immunity from the mother
▪ Acquire IgG by two routes that rely on neonatal Fc receptor (FcRn):
• Placenta while in uterus
• Gut after ingestion of mother’s colostrum
Mechanism of immune evasion
- antigenic variation
- inhibition of complement activation
- blocking by hyaluronic acid capsule
Is there memory with passive immunity
No
Whole vaccines
• Killed whole bacterial cells or inactivated virus • Live, attenuated bacterial cells or virus
Acellular or subunit vaccine
Antigens derived from bacterial cells or virus particles
• Typically, surface molecules or neutralized toxins (toxoid)
Recombinant vaccine
Genetically engineered
• Selected genes for microbial antigens are cloned into a vector
Whole vaccines: killed or inactivated
- Stimulate a weaker immune response: Humoral only
- boosters
Live attenuated vaccines:
Stimulate a strong immune response: Humoral + CMI • Require fewer doses and booster shots
• Require refrigeration, more difficult to transport
• Possibility of reversion (back mutation to wild type)
Toxoid vaccines
acellular): formalin treated bacterial toxins
• Diphtheria, Tetanus, and acellular pertussis (DTaP)
Conjugate vaccines
encapsulated bacteria (incapable of activating CMI) • Capsular polysaccharide molecule conjugated to protein (usually a toxoid) ✓Ensures CMI with class switching • HaemophilusinfluenzatypeB(Hib) • Streptococcuspneumonia,pneumococcalconjugate(PCV13) ✓13 capsular serotypes ✓Indicated for use in infants • Neisseriameningitidis
Subunit vaccines:
viral components • Hepatitis B surface antigen
• HPV
✓9-valent vaccine (released 2015)
Recombinant vector vaccines
-Selected genes for microbial antigens are cloned into a vector
• Vaccinia virus, Canarypox virus, attenuated polio virus, adenovirus
• Attenuated Salmonella, Mycobacterium bovis (BCG)
• The cloning host will produce the antigen for use in a vaccine
DNA/RNA vaccines
DNA plasmids encoding antigenic
proteins injected into patient
• Expression of foreign proteins in host cells
• Strong humoral and cell-mediated response
When can you give fetus and neonates live attenuated vaccines
After 12 months
