CATIE IMMUNOMODULATORS: Friendly bacteria - helping the immune system

IMMUNOMODULATORS: Friendly bacteria - helping the immune system

TreatmentUpdate40: (CATIE) - February 1993
Sean Hosein

All humans have friendly bacteria living in their intestines producing vitamins which they absorb. These friendly bacteria also help to keep the growth of harmful yeasts under control. Although the bacteria can directly attack other microorganisms, friendly bacteria may also help the immune system. It is known that as humans age the effectiveness of the immune system declines. In people with HIV infection, ageing is another factor which may make older people less resistant to the effects of HIV infection. Researchers in Italy have been conducting experiments on elderly humans using friendly bacteria. Results from their experiments suggest friendly bacteria may help improve some immunofunctions.

SUBJECTS AND BACTERIA

The researchers enrolled 25 healthy subjects who were at least 70 years old. Subjects were randomly assigned to receive capsules of friendly bacteria (2 capsules 4 times daily) or placebo. Capsules containing millions of bacteria (brand name Infloran(R)) were supplied by the Instituto Sieroterapico Berna in Como, Italy. The bacteria inside the capsules were Bifidobacterium bifidum and Lactobacillus acidophilus. Fifteen subjects received bacteria and 10 were given placebo.

RESULTS

The researchers found that there were no significant changes in T-cell numbers or side effects as a result of receiving the bacteria. However, subjects given bacteria had statistically significant increases in the number of B-cells compared with others who received placebo. There were no changes in other types of blood cells. In subjects who had inflammation of their intestine, use of friendly bacteria decreased the inflammation by 50% compared with subjects on placebo who did not have a reduction in inflammation. Along with the reduction in inflammation, the numbers of white blood cells in those tissues were reduced in subjects given bacteria. This marked withdrawal of white blood cells (which were no longer needed) in those given bacteria compared to those given placebo was statistically significant.

HOW BACTERIA CAN HELP

Use of friendly bacteria may produce a "barrier" against other, less welcome microorganisms. In experiments with animals, oral use of bacterial products have been found to stimulate the immune system. This is why some vaccines can be given orally. For people with HIV infection, friendly bacteria may be one way to keep the growth of yeast such as Candida in check. High doses of bacteria, such as those used in this study, have potential to increase levels of antibody-producing B-cells and perhaps delay the appearance of life-threatening diarrhea caused by C. parvum, commonly called 'crypto'. More information on this is presented in the section on infection fighters.

REFERENCES:

1. DeSimone C, Ciardi A, Grassi A, etal. Effect of Bifdobacterium bifidum and Lactobacillus acidophilus on gut mucosa and peripheral blood lymphocytes. Immunopharmacology and Immunotoxicology 1992;14(1 & 2):331-340.

2. Kendig NE, Chrest FJ, Nagel TE, et al. Age-related changes in the immune function of HIV-1 seropositive adults . Aging:Immunology and Infectious Disease 1991;3(2):67-80.

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