Intestinal microflora: probiotics and autoimmunity

Nutrition, geoepidemiology, and autoimmunity

As well represented by the impaired immune function of malnourished individuals encountered in developing countries and the incidence of specific diseases following local nutrient deficiencies, nutrition and immunity have been linked to each other for centuries while the specific connection between dietary factors and autoimmunity onset or modulation is a more recent acquisition. Autoimmune diseases manifest limited prevalence rates in developing countries while numerous immunity-related claims have been proposed in the field of functional foods. Nevertheless, over the past years multiple lines of evidence have supported a major role for specific dietary factors (including vitamin D, vitamin A, selenium, zinc, omega-3 fatty acids, probiotics, and flavanols) in determining the immune responses involved in infections, allergies, and autoimmune diseases. Interestingly, the link between nutrition and autoimmunity may well contribute to the geoepidemiology observed for numerous conditions. In general terms, most data that will be discussed herein were obtained in experimental or animal models while human data from real-life clinical settings or randomized clinical trials remain largely unsatisfactory. Our current knowledge on the beneficial impact of nutrition on autoimmunity prompts us to encourage the search for evidence-based nutrition to support the everyday diet choices of patients.

Influence of probiotics on Candida presence and IgA anti-Candida in the oral cavity

Probiotics are defined as microorganisms that promote benefits to host health, mainly by regulating resident microbiota. Disequilibrium in microbiota can favor the growth of opportunist microorganisms and the development of pathologies, like candidosis caused by yeasts of the Candida genus. This work evaluated whether probiotics consumption was able to influence a specific immunological response to Candida and the presence of these yeasts in the oral cavity. Saliva samples were collected from healthy individuals and plated in Dextrose Saboraud Agar with chloramphenicol. Individuals presenting Candida in the oral cavity used the probiotic Yakult LB® for 20 days, after which new collections and identifications were performed. Anti-Candida IgA analysis was conducted using the ELISA technique. Analysis of the results showed a significant reduction in Candida prevalence (46%) and mean Candida CFU/mL counts (65%). The Candida species identified were C. albicans (98%) and C.tropicalis (2%), before and after probiotics consumption. Immunological analysis demonstrated a significant reduction in anti-Candida IgA levels after probiotics use, probably due to less antigenic stimulation. In conclusion, in the individuals studied, probiotics use significantly reduced the amount of Candida in the oral cavity, possibly due to competition between the yeasts rather than by specific secretory immune response stimulation.

Probiotics and autoimmunity: an evolutionary perspective

Probiotics are microorganisms that have demonstrated beneficial effects on human health. Probiotics are usually isolated from the commensal microflora that inhabits the skin and mucosas. We propose that probiotics represent the species of microorganisms that have established a symbiotic relationship with humans for the longest time. Cultural practices of ancient human societies used to favor that symbiosis and the transmission of probiotics from generation to generation. New practices, introduced as a result of industrialization, such as childbirth by surgical delivery, ingestion of pasteurized and synthetic compounds-supplemented food, cleaner homes, indiscriminate use of antibiotics and so on, have led in recent years to the replacement of probiotics by other microorganisms that are not as well adapted to the microenvironments of the human body. These newly settled microorganisms lack many of the beneficial effects of probiotics. Our hypothesis is that the sudden change (from an evolutive perspective) in human intestinal microflora may importantly contribute to the rise in the incidence of autoimmune diseases, observed in the last half a century.