Abstract
There is described defense against various pathogens and tumor cells in this part. The immune system must be able to distinguish between harmful pathogens and microorganisms that are not dangerous.
The method of defense depends on the characteristics of the pathogen. Too strong or long-lasting immune response can cause more damage than the pathogen alone.
For the immune system, it is difficult to recognize the tumor cells which express a number of autoantigens. If they are recognized by the immune system in the defense against them may apply nonspecific and antigen-specific immune mechanisms.
There are also described basic laboratory methods that are used to determine the humoral and cellular components of the immune system. The quantitative or qualitative assays that are based upon the specific reaction of the antigen with the antibody.