Bacteria of human physiological microflora liberate immunomodulating peptides

Microflora-associated defense stimulating factors

Mucosal surfaces are habitats for the physiological microflora and are closely related to the mucosal immune compartment (mucosa-associated lymphoid tissue, MALT). Recently, considerable evidence has accumulated showing that various members of the physiological microflora liberate low molecular weight substances which, apparently, are essential for the adequate immune response of the host. Antibiotic decontamination (e.g. of the BALB/c mouse gastrointestinal tract) results in a lack of generation of immunopriming microbial substances leading to immunosuppression. Biochemical analysis of the microbial substances revealed reproducible chromatographic fractions which selectively influence maturation, proliferation and activation of mononuclear immune cells.

The polybacterial lysate Olimunostim modulates lymphocyte function in vitro and restores depressed cellular immunity in vivo

Immunobiological activity of the polybacterial lysate Olimunostim (P. acnes, K. pneumoniae, S. aureus) was examined by investigating its effects on murine lymphocytes. When added to in vitro lymphocyte cultures, Olimunostim induced interleukin-2 (IL-2) biological activity (in a 2-d culture) and subsequently potentiated lymphocyte proliferation (on day 3); the latter effect was dependent on the presence of adherent cells. In vivo, significant enhancement of lymphocyte reactivity to T-mitogens and increase of CD4+ helper-inducer T lymphocytes were observed 3 d after a subcutaneous application of Olimunostim to mice with cellular immune deficiency. These results confirm the modulatory properties of Olimunostim towards lymphocytes both in vitro and in vivo, which may form a basis for its clinical application.

Modulation of the intestinal microflora by the non-absorbable antibiotic vancomycin leads to a reduction of the tumor load in liver and spleen in a leukemic rat model

Based on previous studies where it was shown that non-absorbable antibiotics can influence the normal hematopoiesis via changes in factors related to the intestinal microflora, the influence of vancomycin on the progression of acute myeloid leukemia was investigated in the BNML rat model. Oral vancomycin, which selectively reduces Gram-positive bacteria in the gut, leads to diminution of the leukemic load in liver and spleen by 30-60%. This 'antileukemic effect' is not dependent on Gram-negative bacteria as source for endotoxin. The presumed mechanism is a decrease of the leukemic growth fraction caused by alterations in the absorption of substances from intestinal Gram-positive bacteria.

Propionibacterium acnes-metabolites inhibit experimental lung metastasis of murine sarcoma L-1 in BALB/c-mice

Adhesive interactions between tumor cells and host tissue occur at several stages of metastasis. Such interactions might be inhibited by microbial metabolites resembling the binding regions of matrix molecules. Certain metabolite sequences including Gly, Asp, Arg, and Ser (GAAS) proved to be critical for cell interactions, e.g. with fibronectin. In vitro, the rosette formation of murine pulmonary cells and sarcoma L-1 cells decreased significantly in the presence of Propionibacterium acnes-metabolites rich in GAAS. In vivo, coinjection of Propionibacterium acnes-metabolites and sarcoma L-1 cells significantly inhibited the formation of lung colonies in BALB/c mice. The inhibition of lung colonization by these metabolites appeared to be noncytotoxic and obviously did not result from impairment of cellular tumorigenicity.

Thymocyte proliferation and maturation in response to staphylococcal lipoteichoic acid

Lipoteichoic acid (LTA) from Staphylococcus saprophyticus strain S1 could be shown to induce thymocyte proliferation and maturation in BALB/c-mice after systemic administration. The increase in thymocyte numbers per mg organ weight was statistically significant. Determination of thymic lymphatic subsets revealed a considerable up-regulation of mature cells expressing helper/inducer (L3T4) or cytotoxic/suppressor (Lyt-2) phenotypes. Thus administration of staphylococcal LTA obviously accelerated murine thymocyte proliferation and maturation. Counts of BALB/c-mouse peripheral blood lymphocytes (PBL) revealed no evident fluctuation within one week after LTA administration, however, statistically significant increases could be detected two weeks after treatment. The determination of activated PBL expressing IL-2 receptors suggested that injection of staphylococcal LTA apparently induced an immunostimulation since those cells were significantly enhanced within one week after LTA administration.