**Probiotics and Immunity**

Marieta Georgieva, Kaloyan Georgiev and Peter Dobromirov

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/61337

#### **Abstract**

Probiotics are "living microorganisms" which exert a prophylactic and therapeutic ef‐ fect by improving the internal microbial balance. Probiotics play a role in defining and maintaining the delicate balance between necessary and excessive defence mecha‐ nisms including innate and adaptive immune responses. The beneficial effects of pro‐ biotics have been demonstrated in many diseases.

New therapeutic approaches toward several inflammatory diseases are being devel‐ oped by affecting the microbial composition of the gut immune system. They are based on the fact that this part of immune system is influenced by many factors, in‐ cluding dietary components and commensal bacteria. An understanding of the molec‐ ular mechanisms behind the direct and indirect effects on the gut immune response will facilitate better and possibly more efficient therapy for diseases, although probi‐ otics (live microorganisms) have already shown promise as treatments for several dis‐ eases in both clinical and animal studies.

Further, the concept of probiotics and the direct and indirect mechanisms by which they can influence gut immunity are described. Emphasis will be placed on the rela‐ tionship of microbiota and the gut immune system.

A review of the history of *Lactobacillus bulgaricus*, probiotics, and probiotic functional foods is made and legislation and modern challenges are discussed.

**Keywords:** Probiotics, immunity, probiotic genomic, history, legislation
