Sometimes pathogens manage to break through the defenses and cause disease. Pathogens can get past this first line of defense - through a break in the skin, for example. O nce inside the body, the pathogen can spread killing off our bodies' cells. In some cases, the pathogens will beat the second line of defense as well. These cells recognise the foreign agents and cooperate to clean out the infection.
B cells produce molecules called antibodies that hook on to pathogens.
Antibodies call out to the other specialized cells, like T cells, to come in and destroy the infecting pathogen. The body's ability to defend itself in this way is called immunity . In some cases, we may not have the necessary antibodies, in which case there are vaccines . In a sense, vaccines are medecine's contribution to the strength of our bodies' immune systems. A vaccine is simply a preparation containing a very weak form of the infectious agent or pathogen.