Naked Science Forum

Life Sciences => Cells, Microbes & Viruses => Topic started by: cjohnson on 05/08/2009 16:59:34

Title: Vaccines
Post by: cjohnson on 05/08/2009 16:59:34

I understand that many vaccines contain live or dead viruses to which the body can develop an antibody response.  My question is, why can the body develop this response to a small or altered exposure of the virus when it can't develop the antibodies after it has been infected?  Is it because the live virus can evade the white blood cells?

Title: Vaccines
Post by: Variola on 05/08/2009 18:35:13

The body does develop the antibodies to whatever infection inveded it, thats why you don't generally get infected twice.The plasma B cells secrete antibodies specific to the antigen/infection, vaccined exploit this by triggering the body into thinking it has been infected, and the  antibodies are made in the same way, but without all the nasty side-effects of the illness.

Title: Vaccines
Post by: cjohnson on 10/08/2009 18:15:44

Thanks.  I hadn't thought about the fact that the body does make antibodies after it is infected in many cases (i.e. chicken pox, flu, etc.)  What I had in mind was Hepatitis B, TB, and HPV - viruses that can be vaccinated against, but are often chronic infections.

Title: Vaccines
Post by: Variola on 10/08/2009 21:17:58

Quote from: cjohnson on 10/08/2009 18:15:44

Thanks.  I hadn't thought about the fact that the body does make antibodies after it is infected in many cases (i.e. chicken pox, flu, etc.)  What I had in mind was Hepatitis B, TB, and HPV - viruses that can be vaccinated against, but are often chronic infections.

Ahh I see what you mean. Well with regards to TB,I know that if a person is vaccinated, against TB, the mycobacterium is dispatched by the anti-bodies quickly before it can do much harm.{I had better note here there are issues with the effectiveness of TB vaccine, but thats the general idea) Otherwise, the person can become infected be asymptomatic, and the mycobacterium can mooch about in the lungs doing what they do. The immune system will deal with them, and the lungs form granulomas round the bacteria, and the lymphocytes kill off the bacteria from inside the granuloma. However the bacteria are not always killed off and they beome dormant, causing a latent infection. Another side effect of this is the cell death from inside the granulomasm causing the characterisic white 'tubles' seen on x-ray. The mycobacterium is notoriously difficult to get rid off, requiring long courses of anti-microbials. So in the case of TB its not that they invade the white blood cells, its that they are difficult to get rid off. I am not as sure about Hep B, although I suspect its the same type of difficulty in getting rid of the virus.