A SHORT HISTORY OF IMUREGEN - AN ORIGINAL TISSUE EXTRACT

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Mil. Med. Sci. Lett. (Voj. Zdrav. Listy) 2019, 88(3), 115-120
ISSN 0372-7025 (Print)
ISSN 2571-113X (Online)
DOI: 10.31482/mmsl.2019.008
REVIEW ARTICLE
A SHORT HISTORY OF IMUREGEN – AN ORIGINAL
TISSUE EXTRACT
Klara Kubelkova and Ales Macela
Department of Molecular Pathology and Biology, Faculty of Military Health Sciences, University of Defence,
Trebesska 1575, 500 01 Hradec Kralove, Czech Republic
Received 14th March 2019.
Accepted 29th April 2019.
Published 6th September 2019.
Summary
Imuregen is a unique dietary supplement that was developed by leading Czech immunologists, made
and distributed from the Czech Republic, and first came out in the 1950s. Imuregen boasts of decades
of research and clinical exposure. It was created for the immune system sourced only from all natural
ingredients that support cellular immunity and energy, tissue regeneration, wound healing, endocrine gland
repair, intestinal integrity, memory enhancement, and has antitumor effects.
Key words: tissue extract; biological response modulator; Imuregen; Retisin
Introduction
Natural biological products in the forms of teas or extracts were the first drugs for improving the fitness of human
beings in ancient times. Over the course of the millennia, an immense amount of empirical experience has been ac-
cumulated. As passed from generation to generation, this has given rise to numerous innovative therapies. Their usage
continues up to the present day, especially in the forms of prebiotics, probiotics, and/or nutritional supplements
to support regeneration or innate immune responsiveness during unspecific sicknesses or during convalescence
from infection or cancerous illnesses. The U.S. National Library of Medicine defines the term “tissue extracts”
as: “Preparations made from animal tissues or organs (animal structures). They usually contain many components,
any one of which may be pharmacologically or physiologically active. Tissue extracts may contain specific, but
uncharacterized factors or proteins with specific actions”(1). In terms of their composition, activity, and largely
uncharacterized nature, a number of extracts of both plant and animal origin which originated in the middle
of the 20th century in former Czechoslovakia fit this description.
Historical aspects
The EKO factory in Prague established an experimental Retisin (RTN) team in the 1940s. It was a small team
composed of external and internal specialists collaborating on a project oriented toward the preparation of animal and
plant tissue extracts directed against tumors. The results of that team’s experiments were classified as secret and the team
members also were bound to secrecy. The founder of the team and its leader was Bohumir Rakusan (1900–1969),
Since 1925
University of Defence, Faculty of Military Health Sciences, Department of Molecular Pathology and Biology,
Trebesska 1575, 500 01 Hradec Kralove, Czech Republic
klara.kubelkova@unob.cz
+420 973 255 193
+420 973 253 100

and its other members were Jaroslav Fanta, Karel Osvald, Gabriel Urbanek, Alois Vystrcil, and Bedrich Dolezel.
The RTN team was oriented toward the preparation of tissue extracts that could be classified as what we more
recently would term biological response modifiers. Several of the tissue preparations were named and patented
(RTN33 – RETISIN (2), RTN112 – LYASTIN (3), RTN121 – SILEXIL (4)).
Retisin was an ethanol extract of bovine tissue. It consisted of 0.5 mg of dry extract per milliliter of double-
distilled water. Its developers had declared the active substance to be a color complex and its sodium salt to be
water soluble. Retisin was patented on 10 October 1946. The trademark expired on 10 October 2006. Lyastin
(RTN112) was an ethanol/ether extract from bovine tissue, and it was declared to be a preparation containing
specific phospholipid and proteolipid components. The trademark for registration of the Lyastin preparation was
issued on 5 November 1941 and expired on 5 November 2001. Among the other preparations prepared and tested
by the RTN team were Silexil, an ethanol extract from milt and roes of herring. Another ether extract, named
Sangitin, came from that same source. A preparation known as Floristen (5) was prepared from Hypericum
perforatum by ethanol extraction. Additional, unnamed, preparations were RTN119 and RTN 134, prepared by ethanol
extraction of bee’s honey. Retisin, Floristen, Lyastin, and other extracts were broadly tested in experiments using
various experimentally induced illnesses on experimental animal models (mice, rats, guinea pigs, and rabbits)
as well as in clinical practice (6-12). In general, Retisin in experimental animal models has been shown to limit
the induction and growth of benzpyrene-induced sarcomas, and the majority of testing teams have shown an anti-
inflammatory effect. Clinical testing at the time had revealed positive effects of the tested preparations and that
these could be utilized as drugs for supportive therapy. Specifically, Retisin was utilized as a supplement to therapy
for oncological illnesses in gynecology, post-irradiation complications in oncology, and as an analgesic (13).
A significant conclusion emerging from the original experiments was that these extracts, namely Retisin and
Lyastin, were effective against tumor cells within in vitro cultures and that they were harmless for nontumor cells.
Such data may still be interesting for formulating strategy to restrict tumor growth.
The EKO factory came under Communist national administration in 1948, and all movable property and real
estates were nationalized and transferred under the state-owned company Biogena. All rights to technical
documentation, research, and patents to RTN preparations were transferred to the national pharmaceutical company
SPOFA (14). The research on RTN preparations was in fact never properly completed. Some of the preparations,
among them Retisin, as the predecessor of the products Juvenil and Imuregen, were put into production on the basis
of a political decision in 1958. They were manufactured in injection form until the late 1970s. Finally, Retisin,
as well as some other original extracts prepared by the RTN team, was eliminated from production in 1975 under
so-called “Action Mars,” which had been intended to modernize the assortment of drugs in the Czechoslovak health
care system (15). The decision of the Ministry of Health on Retisin stated that: “the preparation has only
a symptomatic effect, it could hide the course of the disease itself - production is stopped” (16).
The worst accident in the history of nuclear energy occurred during a technical test at the Chernobyl nuclear
power plant in northern Ukraine on Saturday, 26 April 1986. Responsible persons in the Soviet Union sought ways
to protect the affected population from the consequences of radiation exposure. The original Retisin, and the result
of its renewed production under the name Juvenil, along with Silexil, were tested for harmlessness and efficacy
at several laboratories in the Soviet Union and Poland (17). Subsequently, Retisin, now renamed Juvenil, was tested
also in the laboratories of several Czechoslovak institutions. The Center of Nutritional Hygiene declared that: “Juvenil
is medically harmless. However, according to the method of ‘rejuvenating tissue therapy’ proposed by prominent
Soviet biologist professor Vladimir Filatov, Juvenil does not show extraordinary biological stimulating effects.”
All the results from Juvenil testing by the institutions mentioned above were evaluated and interpreted in conformity
with Filatov’s theory of so-called ,,external therapy” according to which those substances that are produced in large
quantities during decomposition or destruction of tissues have a large stimulatory effect when absorbed through
the skin.
Juvenil was tested also at the Techonin Research Laboratory of the Purkyne Military Medical Academy, Hradec
Kralove, Czechoslovakia. The military experts, based on the data from original testing, suggested that the Juvenil
preparation is a biological response modifier and not merely a nutritional supplement or “rejuvenating” preparation.
For this reason, Juvenil was tested according to the published “Multistep scheme for testing immunomodulatory
Klara Kubelkova and Ales Macela: History of Imuregen
116

substances”(18). The results were summarized in a research report dated 12 June 1989 (19). According to the results
of the test utilized for Juvenil, the preparation has no mitogenic activity when tested in vitro on murine spleen cells.
When given in vivo per os to mice (seven consecutive days), Juvenil significantly increases the readiness of lymphoid
cells (T and B lymphocytes) for response to mitogen (the test was carried out 24 h after the last administration
of Juvenil). In a co stimulatory test, however, Juvenil generally and significantly interfered with the activity of Con
A (T-cell mitogen) in the same T-cell subtypes. The co stimulation with PHA (another T-cell mitogen) and LPS
(a B-cell mitogen) was rather negligible, if any occurred at all. Juvenil was tested also for its potential ability
to initiate the activity of cytotoxic cell populations, specifically, the activity of natural killer cells (NK cells) and
macrophages. The results of both tests revealed the ability of Juvenil to induce NK cell activity against NK cell-sensitive
cellular targets as well as to induce cytotoxicity of murine peritoneal macrophages against two different standard
target cell lines. The preliminary results also demonstrated that Juvenil administered in vivo increased resistance
to mild pathogenic bacteria, but its effects against fully virulent bacteria were negligible. Based on the initial results,
a change was recommended in Juvenil’s administration form from that of liquid drops to pills. The pills, under
the name Stimunal, were tested against infection with two strains of the intracellular bacteria Francisella tularensis.
The preliminary results revealed protective effect only against the strain with very low virulence [20].
In parallel with examining the immunomodulatory activity of Juvenil, and in accordance with the general task
originally assigned to evaluate induction of resistance (protection) against γ irradiation (Co60), the material was
tested on mice. These experiments were done at the Department of Radiobiology, Purkyne Military Medical
Academy, Hradec Kralove, Czech Republic. This series of experiments was never finalized due to a reorganization
of the Academy. From preliminary evaluation of radioprotective effect, however, it can be said that Juvenil probably
influences the redistribution of stem cells among bone marrow, spleen, and periphery. Thus, important information
about several basic characteristics in functional profile for the ethanol or ethanol/ether extracts of bovine tissue
were accumulated up to the late 1980s.
The last decade of the 20th century brought essentially a rebirth for this interesting preparation. This was due
to an increased interest within Central Europe in alternative medicine and natural products, including in natural
dietary supplements that might eliminate the impacts of technological and civilization stressors on the health
of the human population. The company Uniregen, Ltd. in Nachod, Czech Republic, prepared a new batch of the bovine
tissue extracts under the original formula, renamed it Imuregen, and invited several expert groups from different
institutes to participate in reevaluating the biological effects of Imuregen.
The first information from this era can be obtained from the final research report of the project “Protective and
immunomodulative influence of supplementing DNA: comparing of clinical testing and experimental model,”
financed by the Internal Grant Agency of the Ministry of Health of the Czech Republic (21). The Health Institute,
Usti nad Labem; Microbiological Institute of the Czech Academy of Sciences, Prague; Medical Faculty of Charles
University, Prague; and Institute of Anatomy, Medical Faculty of Charles University, Hradec Kralove (all in the Czech
Republic) participated in the aforementioned project. Immediately when new testing began, a discussion began
on how to interpret the results of the model studies. There were only two working hypotheses considered in evalu-
ating the results of the studies. These related to (1) the effects of nutritional supplementation due to the nucleotides
and other low-molecular weight components within the extract, and (2) as a result of the already mentioned
modulation of biological responses, mainly the question of whether the material participates in the innate immune
responsiveness. There may in fact be no essential difference between these two views on molecular interactions,
because both are causing functional changes in the evaluated cell systems.
The results of the aforementioned research project demonstrated in a murine model that a 30-day preventive
application of Imuregen in the form of a drinking regime substantially increased levels of regulatory cytokines, and
especially of those which are important for the development of antitumor immunity. In parallel, the work revealed
stimulatory effects on the differentiation and activity of cytotoxic T lymphocytes and NK cells. The same experimental
setup applied to analyzing the effect of Imuregen on antibody-producing cells showed increase in the absolute number
of cells producing IgM and IgG antibodies in the spleens of treated animals. In all experimental arrangements used,
the condition of experimental animals was monitored. From the data thus obtained, it was concluded that for mice
the 30-day drinking regime of Imuregen showed no evidence of toxic effects. Histological examination of gut epithelium
proved a positive influence of Imuregen on regeneration and growth of terminal ileum epithelium.
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Klara Kubelkova and Ales Macela: History of Imuregen

Field experiments focused on preventive application of Imuregen as a nutritional supplement were conducted
in three blocks: supplementation of preschool children, school children, and senior population. In all three blocks
there was demonstrated significant reduction in sickness, decreased morbidity, and significantly fewer sick days (21).
During clinical testing, nutritional supplementation with Imuregen demonstrated significant change in laboratory
parameters and improvement in clinical indications of symptoms among patients with chronic fatigue syndrome.
In children with allergies, Imuregen improved the clinical and laboratory parameters. It should be noted that,
in this case, there had been an interaction of two independent treatment methods, including a combination
of speleotherapy and Imuregen supplementation. Noteworthy is that the effect of Imuregen supplementation was
superior to that of speleotherapy itself. The results of the project also proved that supplementation with Imuregen
contributed substantially to reparation of immune functions in sick persons affected by ulcerative colitis. The majority
of the project’s results were published in scientific journals with strict peer review policies (22-24).
Based upon the results obtained thus far, Imuregen is recently being combined with other biological response
modifiers, such as Pleuran, which is an agonist in the trained immunity, and/or other natural, biological products
(biological fibers, Ginkgo biloba, minerals or vitamins) that can constitute effective nutritional, metabolic,
or cognitive enhancers. All the information on the functional profile of Imuregen presented in this short history
has demonstrated the versatility of Imuregen’s actions, which, moreover, reflect the definition of a tissue extract.
As a complex of biologically active low molecular weight components, Imuregen constitutes a versatile
modulator of biological responses. In accordance with recent information on the broad spectrum of Imuregen’s
biological activities, it can be said in summary that individual active Imuregen components seem to be distributed
into different tissue compartments of the body where they interact directly with the cells there. The direct interaction
of the components can be facilitated solely by such of their basic molecular characteristics as molecular weight,
charge, and/or primary sequence of component construction units (amino acids and/or nucleotides). These can be
ligands for cell surface receptors or signals for so-called damage-associated molecular pattern receptors. Subsequent
to interaction, individual components may induce changes in activation of cellular signaling pathways that influence
the functional profile of responding cells and, in parallel, influence the intercellular signaling that controls the tissue
microenvironment and, directly, the parameters of response to stressors (Fig. 1).
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Klara Kubelkova and Ales Macela: History of Imuregen
Figure 1. Imuregen – a complex of biologically active compounds. The components of Imuregen, after their distribution to relevant
targets, can function as a nutritional supplement in support of cell nutrition when some corresponding biologically active molecules
are missing in the body of the Imuregen recipient (A). Once selectively distributed, the components of Imuregen, and in our view
specifically the oligopeptides and nucleotides, constitute various ligands for cell receptors and, after ligation, initiate signals
controlling the target cell behavior (B). The cell response subsequently initiates the microenvironment by changes in the metabolic
and secretion profiles (C). Finally, all these changes dictate the functional profiles of cellular systems for individual organs (D).
DC
B
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immune r ocessespreparationr
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Modulation of
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A

Conclusion
Such is the short history of one of the original preparations emerging in the Czechoslovakia. Nontoxic
and apparently free of side effects, Imuregen and Imuregen-derived products seem to be promising tools
for mitigating various stressor influences such as infections, different types of irradiation, some immunological
disorders, and nonlethal deviations in the metabolism. Due to the broad spectrum of the tissue extract’s
modulatory activity, however, such preparations must be utilized only to a reasonable extent and, in cases
of disease, consultation with one’s doctor or pharmacist would be advisable. Meanwhile, a product demonstrating
such promising broad modulation of biological responses deserves further targeted research to uncover
the molecular basis of its effects.
Author contributions
All authors contributed equally to the work.
Funding
This work was conducted within the framework of Ministry of Defence of the Czech Republic - long-term
organization development plan Medical Aspects of Weapons of Mass Destruction of the Faculty of Military Health
Sciences, University of Defence.
Conflict of Interest
The authors declare that they have no conflicts of interest regarding the publication of this article.
Adherence to Ethical Standards
This article does not contain any studies involving animals performed by any of the authors.
This article does not contain any studies involving human participants performed by any of the authors.
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