An improved immune system can selectively wipe out the invading microbes without adversely affecting other cells. Neem not only enhances antibody production but also seems to improve the cell-mediated immune response by which white blood cells are unleashed to kill the invaders. In this type of immune response, special scavenger cells in the blood called macrophages devour the microbes and present bits of them along with their own surface molecules. By enhancing the body's first line of defense, neem helps the immune system more quickly respond to infections that might otherwise gain a strong foothold that would then be more difficult to overcome. Neem, especially neem bark , is recognized for its immunomodulatory polysaccharide compounds.
Neem oil acts as a non-specific immunostimulant that activates the cell mediated immune response.
This then creates an enhanced response to any future challenges by disease organisms. When neem oil was injected under the skin there was a significant increase in leukocytic cells and perioneal macrophages showed enhanced phagocytic activity and expression of MHC class II antigens. Production of gamma interferon was also induced by the injection. Spleen cells showed higher lymphocyte reaction to infection but did not augment anti-TT antibody response. By enhancing the cellular immune response most pathogens can be eliminated before they cause the ill feeling associated with disease.