The Third International Symposium on Transfer Factor was held October 12- 14, 1978, at the Wadley Institutes of Molecular Medicine, Dallas, Texas. Progress in several areas was reported: The animal models that were tentative a few years ago have been defined and extended by several groups. Promising models in mice and cattle were described. In mice, although the assays are somewhat lacking in sensitivity, there were several instances in which there was evidence that the transfers from immune donors to naive recipients were antigen specific; however, when large doses of transfer factor were given, specificity was lost. The activities of transfer factor-containing dialysates have been examined in several species. Human leukocyte dialysates were shown to cause conversion of rat thymocytes from the cortisone-sensitive to the cortisone-resistant state. Addition of these dialysates to PHA-stimulated thymocytes increased thymidine incorporation. Preparations from human and bovine lymphoid tissues were given to mice, and the spleens of the recipients were then examined for antigen-reactive cells in a cell proliferation assay. Enhanced antigen-specific responses were seen in about 30% of the recipients, about 40% had suppressed responses, and no effect was seen in the remaining mice. Immunomodulating effects were also seen in guinea pigs that were given either tolerizing or sensitizing doses of ABA-tyrosine (ABA-T), or tolerizing doses of the antigen in leukocyte dialysates. In contrast to the tolerant animals, the recipients of antigen and dialysate had flare-type skin responses and could be sensitized with ABA-T in complete Freund’s adjuvant. In mice, a rich source of transfer factor activity was the nonadherent, PHAresponsive, B-positive lymphoid cells from nylon wool columns. Activity was also found in the adherent cell populations, but these preparations were contaminated with about 20% B-positive cells. While there has not been a detailed analysis of interspecies restrictions on sensitization with transfer factor, considerable evidence suggests that they do not exist. Human preparations have activity in mice and cattle, and bovine and murine preparations are active in mice and men. The results of experiments with high-pressure liquid chromatography and enzymatic degradations (Table 1) from two separate groups of investigators led to tentative structural models of transfer factor. Using transfer of delayed skin reactivity in human volunteers as the assay system, one group found the biological activity to be sensitive to Pronase, protease K, carboxypeptidase A, and phos113 0013-9351179/050113-03$02.00/O Copyright Al1 rights
0 1979 by Academic Press. Inc. of reproduction in any form reserved.
phodiesterase I but resistant to digestion with alkaline phosphatase, phosphodiesterase II, leucine aminopeptidase, chymotrypsin, and ribonuclease A. Somewhat different sensitivities were found when the assay system employed was induction of antigen responsiveness by lymphocytes in vitro as shown by an agarose leukocyte migration inhibition assay. In this system, the activity was found to be sensitive to the same proteases but resistant to phosphodiesterase I and sensitive to phosphodiesterase II; it was also sensitive to alkaline phosphatase, Pl nuclease, and ribonuclease Tl (Table 1). It should be noted, however, that the TF specificities studied in vivo and in vitro differed. The in vivo studies employed TF specific for keyhole limpet hemocyanin (KLH), whereas in vitro TF specific for purified protein derivative of tuberculin (PPD) was characterized. This may explain the discrepancy in enzyme sensitivities, since one might expect different structures for TF preparations transferring cellular immune reactivity to two completely different antigenic structures, consistent with the concept of specificity. A tentative structural model contains inosine (probably as IMP), ribose, a phosphodiester bond, and a peptide. Presumably, the property of antigen specificity is encoded in the peptide component. After administration of transfer factorcontaining dialysates to dogs, guinea pigs, or humans, the plasma of the recipients contained a new component that cochromatographed with IMP and contained TABLE PROPERTIES
Inosine, probably as IMP Sugar (? ribose) Peptide (Fluoropa-reactive) PI Pronase Protease K Carboxypeptidase A Leucine aminopeptidase Trypsin Chymotrypsin Phosphodiesterase I Phosphodiesterase
Alkaline phosphatase Ribonuclease Tl Ribonuclease A Dimerized ribonuclease A Pl nuclease Deoxyribonuclease Phospholipase A2
Present Present Present 1.6
Sensitivea,b Sensitive” Sensitive” ResistanY Resistant”,b Resistant”” Sensitive” Resistantb Resistant” Sensitive’ Resistant” Sensitiveb Sensitiveb Resistant” Resistant”,b Sensitive” Sensitive* Resistant”” Resistant*
n Assayed by transfer of delayed cutaneous hypersensitivity. * Assayed by in vitro induction of antigen responsiveness in leukocyte migration inhibition G. B. Wilson, H. H. Fudenberg, and V. J. Bahm, Trans. Ass. Amer. Phys. 91, 294, 1978.
peptide (Fluoropa-reactive), a sugar, and a phosphate ester. It was also sensitive to Pronase and protease K. Some of the most impressive clinical effects of transfer factor were seen in patients with viral infections such as herpes zoster, recurrent herpes simplex, or measles pneumonia. Good results were observed in some patients with Behcet’s syndrome, but another group reported that only the neurological manifestations of the syndrome improved. No benefits were seen in patients with SSPE, but the cellular immunity of the donors to relevant antigens was not tested. Patients with chronic mucocutaneous candidiasis were treated with transfer factor from donors either sensitive or insensitive to Cundidu. Both groups did better than would be expected from amphotericin B alone, but long-term remissions occurred only in patients who developed and maintained positive delayed reactivity to Candida. A controlled clinical trial in chronic cutaneous leishmaniasis was especially impressive. Recipients of transfer factor from Leishmuniu-sensitive donors showed healing in 10 of 12 instances, while only 3 of 13 recipients of transfer factor from insensitive donors healed. There were no responders in the placebo group. Other discussions dealt with such practical problems as standardization of methods and terminologies in various laboratories. The definition of a “unit” of transfer factor was suggested as the material obtained from lo* lymphocytes, pending development of more precise chemical or immunological assays. Other discussions dealt with definition of an “effect” of transfer factor; i.e., whether this should be limited to skin test conversion or whether other measurements, such as enhancement of T-cell rosette formation or induction of lymphokine production in vitro, are also acceptable. Agreement in this area is not possible at present, since no laboratory has enough experience. However, any system used must be capable of detecting antigen-dependent specific transfer or induction of cellular immunity, since this is a characteristic of TF by definition. This limitation by itself allows one to predict successful use of lymphokine production in vitro but not enhancement of T-cell rosette formation, since the former is antigen dependent, while the latter is not necessarily so. However, once the data are adequate to permit a decision, it should be possible to define a “minimal effective dose” for use in clinical trials. CHARLES H. KIRKPATRICK National
Laboratory Institute of Allergy
of Clinical Investigation and Infectious Diseases Bethesda. Maryland 20014
AMANULLAHKHAN NORWOODO.HILL Wadley
of Molecular Dallas,
Medicine TX 75235