Antibody formation: initiation in "nonresponder" mice by macrophage synthetic polypeptide RNA

Failure of synthetic polynucleotides to affect the immunogenicity of mycobacterial ribonucleic Acid and ribosomal protein preparations

The synthetic polyribonucleotides adenylic acid (poly A), uridylic acid (poly U), cytidylic acid (poly C), and inosinic acid (poly I), whether single- or double-stranded (poly A:U, poly I:C), cannot replace mycobacterial ribonucleic acid (RNA) in the production of a high immune response in CF-1 mice against tuberculous disease. These conclusions are based on the results of several types of experiments. (i) Poly A and poly U, used either singly or in combination, did not increase the immunogenicity of mycobacterial RNA preparations whether emulsified in Freund's incomplete adjuvant (FIA) or not emulsified. (ii) Mycobacterial ribosomal protein, extracted with 2-chloroethanol, was not immunogenic; the addition of poly A:U to the protein did not produce an immune response and FIA did not affect these results. (iii) The RNA left after the protein was extracted was partially immunogenic when emulsified in FIA even though it was partially degraded. (iv) Mycobacterial RNA prepared with ethyl alcohol and partially degraded with ribonuclease had a significantly lower immunogenic activity, and the original higher immune response was not restored by the addition of poly A:U. (v) Mycobacterial RNA totally degraded by weak alkali was not immunogenic, the original immunogenic activity was not restored by the addition of poly A:U or poly I:C, and FIA again did not influence the results. These findings suggest that (i) protein, polypeptides, or other antigenic fragments, if present, are not the specific immunogens; and (ii) mycobacterial RNA is responsible for the high immunogenic activity of mycobacterial ribosomal and RNA preparations. In addition, since the double-stranded forms of these synthetic polynucleotides markedly potentiate the formation of circulating antibodies, these results also reemphasize the lack of correlation between conventional antibody formation and immunity against tuberculosis.

Comparative evaluation of the protective effect of immune spleen cells and immune RNA against Plasmodium berghei

Earlier studies from this laboratory indicated that passive transfer of viable or frozen-thawed cells from spleens and lymph nodes of immune mice resulted in a significant protective immunity against Plasmodium berghei in syngeneic recipients. To assess whether immune RNA played a role in conferring such protection, experiments were designed wherein immune RNA was isolated from immune monkeys, rats and mice and transferred to normal mice. The effect of transfer was assessed by challenging RNA-primed animals with Plasmodium berghei. Results indicated that immune RNA failed to confer resistance against P. berghei both in syngeneic and in heterologous systems.

Anti-tumour cytotoxicity of poly(A)-containing messenger RNA isolated from tumour-specific immunogenic RNA

The transfer of tumour-specific cytotoxicity against a murine fibrosar-coma has been demonstrated in vitro using xenogeneic RNA extracted from tumour-cell-immune animals. Poly(A)-tailed messenger RNA from immunogenic RNA was isolated by passage through an oligo(dT)-cellulose column, and evaluated to determine whether the same tumour-specific cytotoxicity could be transferred. Aliquots of normal C3H mouse lymphocytes were treated with poly(A)-containing immune RNA, whole-cell immune RNA lacking poly(A) and total cellular immune RNA. Treated cells were tested in vitro using an adaptation of the Takasugi and Klein microcytotoxicity assay. Percent cytotoxicity was calculted using cells treated with fractions of normal RNA as control. An increase in tumour cytotoxicity was found with poly(A)-containing immune RNA. The optimum dose of poly(A)-tailed immune RNA was estimated as 6.5 microgram of RNA per 4 x 10(6) lymphocytes. Populations of lymphocytes were separated using glass and nylon wool. T- and B-enriched populations were treated with various RNA components. The adherent cell population showed no significant cytotoxicity, whilst treatment of the nonadherent population with poly(A)-tailed immune RNA produced high levels of cytotoxicity.

Transfer of tumor specific immunity with "immune" RNA: prospects for the treatment of human cancer

Ribonucleic acids extracted from specifically sensitized lymphoid cells (I-RNA) have been shown to transfer specific immunoreactivity to normal non-immune lymphoid cells. Evidence for the transfer by I-RNA, of immune responses to tumor-associated antigens of animal and human neoplasms, in vivo and in vitro, is reviewed. Results obtained in our laboratory and in other laboratories indicate that xenogeneic, allogeneic and syngeneic I-RNA extracts mediate specific cytotoxicity to tumor cells, in vitro, and mediate transplantation resistance and tumor rejection responses in vivo. Our results suggest that I-RNA preparations fail to elicit immune responses directed against "self" antigens. By contrast, I-RNA's directed against "non-self" tumor-associated antigens appear to induce lymphocytes to effect specific anti-tumor immune responses. The mechanisms responsible for the failure of I-RNA to initiate immune responses against "self" antigens are not known at present and demand investigation. Preliminary results of a clinical Phase I trial of immunotherapy with xenogeneic I-RNA in selected cancer patients are reviewed. I-RNA might offer promise as a new modality for the immunotherapy of human cancer.

Factors affecting immunogenic activity of mycobacterial ribosomal and ribonucleic acid preparations

By following careful procedures, mycobacterial ribosomal fractions and ribonucleic acid (RNA) prepared by ethyl alcohol precipitation were obtained which have immunogenic activities similar to the viable attenuated H37Ra cells of Mycobacterium tuberculosis from which they were obtained. This comparison was based on the amount of ribonucleic acid (RNA) present. These preparations consisted of approximately 63% RNA and 37% protein; no deoxyribonucleic acid or polysaccharide was detected by chemical tests. A high correlation was found between the immunogenic activity of a preparation and the per cent increase in hyperchromicity at 260 nm of a ribonuclease-hydrolyzed portion. Final concentrations of sodium dodecyl sulfate higher than 0.25% when used for the preparation of the ribosomal fractions and RNA resulted in significantly lower immune responses and greater variation between experiments. This was not related to the amount of protein present. The stability of the ribosomal and RNA preparations was tested under a variety of conditions. The need for a good protective adjuvant again was shown since mouse serum readily hydrolyzed the RNA. Equal immunity was obtained after immunization by the intraperitoneal and subcutaneous routes; however, no immune response was obtained when the intravenous route was used. Preliminary results with RNA prepared with phenol showed that it was more easily degraded during preparation. This resulted in a lower immune response than was obtained with the RNA prepared with ethyl alcohol.

The interaction of human monocytes and lymphocytes

Monocytes isolated from the peripheral blood of tuberculin-positive and tuberculin-negative donors were exposed to PPD, extensively washed, and incubated with autologous or homologous lymphocytes. Lymphocyte transformation was measured morphologically and by incorporation of (14)C-labeled thymidine. Monocytes from tuberculin-positive subjects induced transformation of autologous lymphocytes in 19 of 29 experiments. Studies to define the optimal conditions of exposure to monocytes to PPD and to autologous lymphocytes showed that viable, metabolically intact monocytes are required. A ratio of only 1 monocyte to 100 lymphocytes sufficed to induce transformation; neutrophils were inactive. In general, PPD-sensitized monocytes failed to induce transformation of homologous lymphocytes from either tuberculin-positive or tuberculin-negative subjects. Direct contact between monocytes and lymphocytes was required for consistent transformation, and islands of transforming lymphocytes were observed around a central core of monocytes.

Cellular differentiation of the immune system of mice. I. Separate splenic antigen-sensitive units for different types of anti-sheep antibody-forming cells

Spleen cell suspensions of unprimed donor mice containing precursors of immunocytes have been transplanted into X-irradiated recipient mice. In the presence of antigen (sheep erythrocytes) these precursors, called antigen-sensitive units, gave rise to progeny cells secreting specific antibody. We studied quantitatively the production of cells releasing IgM hemolysins (direct plaque-forming cells), IgG hemolysins (indirect plaque-forming cells), and hemagglutinins (cluster-forming cells). We found that each of these immunocyte populations was distinct, i.e., that cells releasing agglutinins did not, as a rule, release hemolysins, and vice versa. We also found that cell populations secreting IgM hemolysins did not shift, under certain experimental conditions, to the production of IgG hemolysins during the primary immune response. By transplanting graded numbers of spleen cells, we succeeded in limiting to one or a few the number of antigen-sensitive units that reached the recipient spleen. We estimated thereby the frequency of antigen-sensitive units in donor cell suspensions and tested their potential for production of immunocytes of more than one type. Our results indicated that antigen-sensitive units were unipotent for they displayed in the spleens of unprimed donors the same restrictions of function and heterogeneity (antibody-specificity differentiation, antibody-class differentiation) found among antibody-forming cells. Furthermore, antigen-sensitive precursors for direct plaque-forming cells, indirect plaque-forming cells, and cluster-forming cells were detected in the spleens of unprimed mice in different frequencies, i.e., 1 in approximately 10(6), 1 in approximately 7 x 10(6), and 1 in approximately 19 x 10(6) spleen cells, respectively. We concluded that relatively advanced differentiation of potentially competent cells occurs before sheep erythrocyte administration. The relevance of this finding for the broad spectrum of immunologic reactivities and for the heterogeneity of antibody responses to given antigens was discussed.