Why does natural bacteria do not give immunity - (Aug/08/2012 )
Why does natural natural bacteria do not give immunity. Is it possible to get lifelong immunity against bacterial infection?
1)What do you mean not give immunity? How complex are bacteria? how many anti-bacterial vaccines are there (and why)?
2)Yes...
Thanks for reply. There is two phases of infection as active and chronic. In case of chronic infection Bacteria present in body for long still do not give protective immunity, why is that? e.g. Salmonella chronic infection.
Why one time if person get infected he gets full antigen dose of bacteria ( with all antigenic component intact- not like deletion vaccine where some antigenic region may be missing) he has chances of getting infection multiple time in future / chronic infection case.
There are bacterial vaccine in case of salmonella too but they offer limited time protection why not life long protection?
Is it possible to get lifelong immunity against bacterial infection like one in case of small-pox infection what we get?
The smallpox vaccine (vaccinia) only offers protection for about 5 years. Some immunities from vaccines are much longer lived, such as the immunity from tetanus and BCG vaccines, which are both against bacteria. Note that for most vaccines you need repeat exposures to get the full immunity. Just because you have an infection does not necessarily mean that you are exposed to useful antigen, which would have to be on the surface of the bacteria for the body to recognise it...
Usually the lack of immunity is due to a range of factors such as the type of cell wall the bacteria have, and whether it is capsulated and/or intracellular or not, as well as the immune response from the individual.
bob1 on Thu Aug 9 09:00:57 2012 said:
The smallpox vaccine (vaccinia) only offers protection for about 5 years. Some immunities from vaccines are much longer lived, such as the immunity from tetanus and BCG vaccines, which are both against bacteria. Note that for most vaccines you need repeat exposures to get the full immunity. Just because you have an infection does not necessarily mean that you are exposed to useful antigen, which would have to be on the surface of the bacteria for the body to recognise it...
Usually the lack of immunity is due to a range of factors such as the type of cell wall the bacteria have, and whether it is capsulated and/or intracellular or not, as well as the immune response from the individual.
Can you please elaborate "
So when you have an immune response, if you want to effectively clear the infection, the immune cells need to identify the bacterium as a pathogen, not as a commensal part of the normal flora, so they need to be attacking the intact bacterium not phagocytosing all bacteria.
The following is my rough understanding of the nature of an immune response: The initial immune response to infection is the presence of macrophages and neutrophils which engulph the bacteria and spit out chunks of protein, each of which is taken up by an immature B cell, which then produces antibody against that protein, however, the vast majority of these proteins are either internal to the bacteria - so can't act as a recognition for the immune response, or don't produce an enhanced immune response because they aren't particularly immunogenic. There are thousands and thousands of these proteins produced, only a few of which will produce an effective immune response.