This vitamin enhances resistance to infection by increasing phagocytic cell migration and lymphocyte proliferation. It also enhances responsiveness to antigenic stimuli. Deficiencies have been shown to decrease lymphocyte activation, lower lysozyme and complement levels (both important chemicals of the immune system), impair secretory IgA production (especially important in the intestinal tract) and decrease T-cell dependent antibody responses.

Beta-carotene appears to selectively increase T-4 cells, reacts with free radicals and free oxygen to help prevent genetic and cell wall damage, increases tumor necrosis factor, increases activity of macrophage and natural killer (NK) cells. This changes into vitamin A as the body requires it.

Research suggests that supplementation with Vitamin A may reverse post-operative immunosuppression as well as boosting immune responses in the elderly, persons with parasitic infections and persons with high exposure to ultraviolet light.

(Cohen B. et alReversal of post-operative immunosuppression in man by vitamin A. Surg Gynacol Obstet 149:688-92, 1979).

(Rumore MM . Vitamin A as an immunomodulating agent. Clin Pharm. 12 (7) 506-14, 1993).

Vitamin B2: Deficiency results in decreased ability to produce antibodies. This vitamin may be depleted by certain drugs.

Vitamin B5: Deficiency results in atrophy and loss of function of thymus gland.

Vitamin B6: Deficiency inhibits cell-mediated immune functions and antibody production, atrophy of spleen and thymus. Folic Acid: Deficiency impairs lymphocyte function and decreases antibody production.

Vitamin B12: B12 is required for proper lymphocyte function and the production of DNA and amino acids (protein).

(Anderson R, Theron A, Effects of B-Complex vitamins on cellular and hormonal immune functions in vitro and in vivo. Int J Vita Nut Res 24:7-84, 1983).

White blood cells use Vitamin C to combat infections, and in the face of inflammation or microbial challenge, levels of Vitamin C are depleted. Animals — with the exception of guinea pigs — have the ability to manufacture extra Vitamin C in their livers to replete their stores — but humans and their distant rodent relatives lack the crucial enzyme that synthesizes C. Thus, when confronted by stress, we need additional outside sources of Vitamin C.

To determine whether vitamin C can alter the function of the immune system and provide increased protection from viral infection, Susan Ritter, MD, PhD candidate, and Gailen D. Marshall, Jr., MD, PhD, both from the University of Texas Health Science Center, studied the white blood cells of 12 patients before and after each patient took one gram of vitamin C daily for two weeks. Researchers then analyzed the immune cell types present in the blood as well as the ability of these cells to make antiviral compounds.

The number of NK cells (a cell that protects against viruses) in the peripheral blood increased after two weeks of supplementation with Vitamin C. While the number of T cells (also active in antiviral immunity) remained the same, they were more activated following vitamin C supplementation. The T cells also produced significantly more interferon-gama (an antiviral compound) and less interleukin-4 and interleukin-10 (both of which are associated with allergic disease) after two weeks of supplementation with vitamin C.

Researchers concluded that this data suggests an increase in antiviral immunity after two weeks of 1g/day vitamin C supplementation and the possible use of vitamin C to modulate the immune system in people.

(Susan Ritter, MD, PhD, Gailen D. Marshall, Jr., MD, PhD, Vitamin C Effect on Immune System: Study presented at the 60th Anniversary Meeting of the American Academy of Allergy, Asthma and Immunology (AAAAI)).

This vitamin increases resistance to infection, increases antibody levels, stimulates B-lymphocytes and promotes T-4 activity and protects vitamins A, C and B-complex from destruction. It is a free radical scavenger and will protect all cell membranes and genetic material from damage from free radicals.

In a 1997 study, Meydani, et al gave healthy elderly subjects 60 mg, 200mg or 800 mg Vitamin E for 235 days in a double-blind study. While immunoglobulin levels and levels of T and B cells were unaffected, certain clinically relevant indices of cell-mediated immunity improved at the 200 mg dosage level. This suggests that the elderly may benefit from higher levels of Vitamin E than those usually recommended.

(Meydani SN et al. Vitamin E supplementation and in vivo immune response in healthy elderly subjects. JAMA 277 (17) 1380-6, 1997).