Vaccines have long been used to boost the immune system and to confer protection against microbial infections. In contrast, immunotherapy based on ribosomal preparations has been proposed to enhance both specific and nonspecific immune responses (in particular, the mucosal immune defense system) against common respiratory tract pathogens. The aim of this review is to summarize current knowledge on the ability of a combination of four immunogenic ribosomal fractions from different bacteria species and of the extracted fraction from the membrane of Klebsiella pneumoniae to modulate several immune functions. The immunomodulatory activity of the ribosome component is attributed to the presence of highly purified epitopes from cellular fractions obtained by bacterial lysis. The ribosomal preparation is hypothesized to induce a T-dependent immune response consequent network with proliferation of B lymphocytes and production of secretory high-affinity antibodies (in particular, IgA), as well as the creation of a specific immune memory. Indeed, this agent stimulates the activity of macrophages, polymorphonuclear cells, and natural killer cells. The "ideal" vaccine is a highly purified protein bound to a carrier and an adjuvant that enhances the vaccination effect.