From Peyer’s Patches to Tonsils

Summary

Ribosomal immunotherapy has been successfully used since the 1960s to boost the immune system and provide protection against microbial infections. We have investigated both whether and how these immunostimulants behave as natural immunogens in the mucosa-associated immune system.

According to current understanding of the physiology of the mucosal immune response, intestinal Peyer’s patches and the related solitary nodules are the primary inductive sites involved in the immune protection of all mucosal surfaces. Sensitised lymphocytes generated at these sites reach the general circulation through lymphatic drainage and relocate in mucosal areas by means of specialised ‘high endothelial venules’. We hypothesised that orally administered ribosomal preparations would yield sensitised B cells specific for bacterial antigens from the parent strains. These cells should then be detectable in the peripheral blood after ribosomal intake, and identifiable as plasma cells in mucosae-associated tissues after completing their terminal differentiation. Ultimately, specific IgA should appear in secretions.

To this end, we studied the immune responses generated in children and adults after ‘Ribomunyl’ administration, according to various consecutive protocols. The initial hypothesis was confirmed by the identification of specific B cells in the peripheral blood, plasma cells in the tonsillar tissue and specific IgA in the saliva. An animal model involving the use of twin sheep enabled detection of the specific cells in mesenteric and cervical lymph nodes. Analysis of these data indicates that ribosomal preparations trigger the production of lymphocytes specific for both ribosomes themselves and whole bacterial antigens. This supports the fact that small antigenic motifs are carried as partly synthesised peptides on the ribosomal particles. Therefore, ribosomes boost an array of B cells that are specific for many antigenic determinants of the bacteria from which they are extracted.

We were also able to show that the stimulation provided was specific, since no response to other bacteria could be detected. Finally, analysis of the kinetics of this stimulation confirmed that oral immunisation generates rapid and transient secretory responses, building increased numbers of memory cells that are readily available to respond to further challenges by either more ribosomal preparations or potential pathogens.