Use of monoclonal antibodies to analyze peripheral blood and salivary gland lymphocyte subsets in Sjögren's syndrome

Using monoclonal antibodies to cell surface antigens, we studied lymphocyte subsets in 15 patients with primary Sjögren's syndrome. The absolute number of OKT8-positive cells (reactive with T suppressor/cytotoxic cells) was significantly decreased in such patients (353 +/- 186/mm3) compared to age-matched controls (631 +/- 150/mm3) (P less than 0.001). The number of OKT4-positive cells (reactive with T helper/inducer cells) was comparable in both groups (932 +/- 588/mm3 versus 1.073 +/- 290/mm3). The ratio of OKT4/OKT8-reactive peripheral blood lymphocytes was increased (greater than 2.4) in 67% of these patients and ranged from 1.0 to 6.4 (normal = 1.8 +/- 0.3). OKT4-positive cells were the predominant subset in lip biopsy specimens stained with immunofluorescence or immunoperoxidase techniques; the OKT4/OKT8 ratio exceeded 3.0 in all 5 patients examined. In 1 patient with pseudolymphoma, a lymph node biopsy specimen contained 80% T cells with an OKT4/OKT8 ratio of 3.2. Thus, OKT4-positive cells predominated in the peripheral blood lymphocytes as well as in sites of inflammation in primary Sjögren's syndrome. The decreased number of OKT8-positive cells in primary Sjögren's syndrome was probably not caused by circulating autoantibody, since patients' sera did not react with normal OKT8-positive cells. Functional studies using pokeweed mitogen demonstrated that T helper cell activity for immunoglobulin synthesis was contained in the OKT4-positive subset in both normal and patients' peripheral blood lymphocytes. Removal of OKT8-positive cells by complement-mediated lysis did not lead to increased immunoglobulin synthesis or production of rheumatoid factor. The identification of peripheral blood lymphocyte subsets by use of monoclonal antibodies and the relationship of these subsets to tissue infiltrates and autoantibody production provide further insight into the pathogenesis of primary Sjögren's syndrome.

Activation of the classical pathway of complement by rheumatoid factors. Assessment by radioimmunoassay for C4

A simple, sensitive solid-phase radioimmunoassay to quantitate the activation of the classical pathway of complement by rheumatoid factor (RF) is described. RF (purified, in serum or synovial fluid) was bound to reduced and alkylated IgG adsorbed to polyvinyl chloride microtiter plates and reacted with diluted normal human serum (complement). The activation and binding of C4 were quantitated with 125I-Fab'2-anti-C4. Purified, polyclonal IgM--RF was 100- to 1,000-fold more effective than purified IgG--RF in activating complement. The amount of complement activation produced by RF in each of the 57 sera and 2 synovial fluid samples correlated directly with the amount of IgM--RF present. The complement activating abilities of polyclonal IgM--RF in the sera of 15 rheumatoid arthritis patients were homogeneous. This novel technique is readily applicable to the investigation of complement activation by RF in disease.

Synovial fluid lymphocytes differ from peripheral blood lymphocytes in patients with rheumatoid arthritis

Peripheral blood (PBL) and synovial fluid lymphocytes (SFL) from 12 patients with rheumatoid arthritis (RA) were analyzed using monoclonal antibodies that detect specific T cell surface antigens (OKT3, OKT4, OKT8, SC1) and antigens associated with lymphocyte activation (anti-Ia, OKT10, B3/25). RA patients' PBL contained 1010 +/- 74 OKT4+ and 401 +/- 62 OKT8+ cells/mm3 (ratio OKT4+/OKT8+ = 2.4 +/- 0.3). In contrast, SFL from these patients exhibited a significantly different proportion of T cell subsets (ratio OKT4+/OKT8+ = 1.1 +/- 0.5) (p less than 0.0001) with 630 +/- 180 OKT4+ and 595 +/- 225 OKT8+ cells/mm3. Synovial fluid contained significantly more activated T cells based on the presence of Ia-positive T cells (19 +/- 5%) and reactivity with antibody OKT10 (49 +/- 7%) compared with RA-PBL (8 +/- 3% Ia-positive T cells and 13 +/- 6% OKT10+). Compared with RA-PBL, normal PBL contained an elevated number of OKT8+ cells (610 +/- 48/mm3), a similar number of OKT4+ cells (1040 +/- 86/mm3), and a lower percentage of activated lymphocytes (3 +/- 2% Ia-positive T cells and 10 +/- 8% OKT10+ cells). SFL, RA-PBL, and normal PBL all showed less than 3% cells reactive with antibody B3/25 (anti-transferrin receptor antibody), a marker found on in vitro activated T cells. These findings demonstrate that the lymphocytes at the site of inflammation differ significantly from the lymphocytes present in the peripheral blood of the same patients. RA patients had a small but significant decrease in the number of OKT8+ cells/mm3 compared with normal PBL (p less than 0.01), suggesting that this lymphocyte subset may home to synovial tissues, where it becomes activated.

Synovial fluid lymphocytes differ from peripheral blood lymphocytes in patients with rheumatoid arthritis

Peripheral blood (PBL) and synovial fluid lymphocytes (SFL) from 12 patients with rheumatoid arthritis (RA) were analyzed using monoclonal antibodies that detect specific T cell surface antigens (OKT3, OKT4, OKT8, SC1) and antigens associated with lymphocyte activation (anti-Ia, OKT10, B3/25). RA patients' PBL contained 1010 +/- 74 OKT4+ and 401 +/- 62 OKT8+ cells/mm3 (ratio OKT4+/OKT8+ = 2.4 +/- 0.3). In contrast, SFL from these patients exhibited a significantly different proportion of T cell subsets (ratio OKT4+/OKT8+ = 1.1 +/- 0.5) (p less than 0.0001) with 630 +/- 180 OKT4+ and 595 +/- 225 OKT8+ cells/mm3. Synovial fluid contained significantly more activated T cells based on the presence of Ia-positive T cells (19 +/- 5%) and reactivity with antibody OKT10 (49 +/- 7%) compared with RA-PBL (8 +/- 3% Ia-positive T cells and 13 +/- 6% OKT10+). Compared with RA-PBL, normal PBL contained an elevated number of OKT8+ cells (610 +/- 48/mm3), a similar number of OKT4+ cells (1040 +/- 86/mm3), and a lower percentage of activated lymphocytes (3 +/- 2% Ia-positive T cells and 10 +/- 8% OKT10+ cells). SFL, RA-PBL, and normal PBL all showed less than 3% cells reactive with antibody B3/25 (anti-transferrin receptor antibody), a marker found on in vitro activated T cells. These findings demonstrate that the lymphocytes at the site of inflammation differ significantly from the lymphocytes present in the peripheral blood of the same patients. RA patients had a small but significant decrease in the number of OKT8+ cells/mm3 compared with normal PBL (p less than 0.01), suggesting that this lymphocyte subset may home to synovial tissues, where it becomes activated.

Histochemistry of NADH diaphorase and gamma-glutamyltranspeptidase in rat bladder tumors

To improve identification of preneoplastic bladder cancer cells, we have studied two enzyme histochemical changes in bladder tumors induced in male Fisher 344 rats by the carcinogen N-butyl-N-(4-hydroxybutyl)-nitrosamine. In early areas of focal nodular hyperplasia there was a dramatic increase in staining for NADH:menadione oxidoreductase (diaphorase)activity. In nonfocal areas as well, there were many individual cells with intense staining, while the controls were of uniform moderate staining. Large papillomas and carcinomas often showed heterogeneous staining. gamma-Glutamyltranspeptidase (GGT) was absent from normal urothelium and from all tumors except the most advanced carcinomas and large papillomas. In old, carcinogen-exposed animals, GGT activity was seen in the luminal surface of tumors and in the interlesion urothelium. In newborn rats and in rats with regenerative hyperplasia following wounding of the urothelium, the diaphorase staining was less than that in the untreated adult. Our findings suggest that increased diaphorase activity may serve to identify early islands of carcinogen-induced, enzymatically altered bladder cells, while GGT will not.

Effect of levamisole on pokeweed mitogen stimulation of immunoglobulin production in vitro

The effects of levamisole (LMS) on immunoglobulin (Ig) production were studied in vitro using peripheral blood lymphocytes from normal subjects stimulated with pokeweed mitogen (PWM). Cells were cultured for 9 days with varying concentrations of LMS and PWM, and immunoglobulin secretion in the supernatants was quantified by solid phase radioimmunoassay. The results showed that 1) the effect of LMS in vitro depends upon the degree of lymphocyte stimulation by PWM. When PWM stimulation is optimal, typical pharmacologic concentrations of LMS (0.5 micro/ml) decrease both IgM and IgG production by 50%. However, at lower suboptimal doses of PWM, LMS, at similar concentrations, enhances immunoglobulin production by 24% (p less than 0.01). Unstimulated lymphocytes are not affected by LMS. 2) The target cell upon which LMS acts is present among a T subpopulation that lacks the Fc receptor for aggregated rabbit IgG (T gamma -negative). We suggest that the diverse effects of LMS on autoimmune disease in vivo may depend upon both the size and degree of activation of the T gamma -negative lymphocyte pool.

Solid-phase selection of human T lymphocyte subpopulations using monoclonal antibodies

This report describes a novel solid-phase technique for the positive selection of human T lymphocyte subsets labeled by indirect immunofluorescence with monoclonal anti-bodies. Fluorescein labeled normal human T cells or a T cell line were fractionated on plastic culture dishes precoated with affinity chromatography purified anti-fluorescein antibodies. Cell binding was specific for fluorescein, and was both time and temperature dependent. Bound cells were eluted at 37 degrees C with fluorescein-L-lysine. The eluted cells were enriched with highly viable and functional human T cell subsets. Thus Leu3 monoclonal antibody selected cells were shown to provide helper activity in the pokeweed mitogen induced IgM and IgG immunoglobulin secretory response of autologous B cells. The Leu2 antibody selected T cells suppressed both IgM and IgG secretory responses. In addition, studies with the monoclonal antibody 1G11, which binds to an antigen expressed on acute lymphocytic leukemia (T-ALL) cells and the T-ALL derived cell line RPMI-8402, demonstrated that this solid-phase technique can be used to select for cells which are present at low frequencies in a mixed population. It thus provides a simple and reproducible means for the preparative isolation of lymphocyte subsets associated with autoimmune and neoplastic disease for functional and biochemical analysis.

Fractionation of human lymphocyte subpopulations on immunoglobulin coated Petri dishes

This report describes a simple solid-phase technique for the positive selection of lymphocytes labeled with fluoresceinated antibodies. B lymphocytes were labeled with fluoresceinated anti-human Ig or monoclonal anti-human Ia (L243), and then were bound to plastic culture dishes coated with affinity purified goat anti-fluorescein specific antibody. Bound cells were eluted at 37 degrees C with 1 mM fluorescein-L-lysine phosphate-buffered saline. Functionally the eluted Ig positive cells responded to pokeweed mitogen (PWM) by in vitro secretion of IgM, as measured by radioimmunoassay of culture supernatants. The secretion of IgM was dependent on the addition of T lymphocytes. Moreover, the isolated B cells were functionally receptive to 'help' and 'suppression' by T cells with and without Fc receptors for IgG respectively. T cell subsets were fractionated on plastic culture dishes coated with heat aggregated rabbit or human IgG. the non-bound cells (enriched T(gamma-)) provided collaborative 'help' in the PWM induced IgM secretion response by human B lymphocytes. The bound cells (enriched T(gamma+)) eluted with 0.01 M EDTA in phosphate-buffered saline, suppressed IgM secretion. This method can be adapted to fractionate subsets of lymphocytes for which a fluoresceinated antibody is available. For routine functional studies, the isolation of cell types with conventional or monoclonal antibodies does not require the use of a fluorescence activated cell sorter, but only an antifluorescein labeled Petri dish. In conclusion, a rapid solid-phase technique enables us to prepare enriched populations of functionally active lymphocytes.

Selective lymphocyte deficiency in seronegative rheumatoid arthritis

Prior studies have shown that in vitro infection with the Epstein Barr virus (EBV) is able to induce IgM rheumatoid factor production by normal lymphocytes, with a higher degree of production by seropositive rheumatoid arthritis lymphocytes. The present investigation demonstrates that EBV-infected lymphocytes from patients with seronegative rheumatoid arthritis produce in vitro significantly less IgM rheumatoid factor than do normal lymphocytes. The results suggest that the peripheral blood of seronegative patients is deficient in the rheumatoid factor precursor B cells responsive to stimulation by Epstein Barr virus.

T lymphocyte-mediated cytotoxicity against autologous EBV-genome-bearing B cells

We have stimulated human peripheral blood lymphocytes in vitro with autologous EBV-infected or noninfected B cells. A cytotoxic response was obtained only when virally infected cells were used. The activity of the effector cells was restricted by the major histocompatibility complex and was directed against EBV-genome-bearing targets. The highest cytolytic response was obtained when lymphocytes of individuals previously exposed to the virus (EBV-VCA positive) were used. Lymphocytes of noninfected donors (EBV-VCA negative) gave a low response; the relative frequency of their effector cells was at least 4-fold lower. Lymphocytes of newborns did not respond. The cytotoxic activity was mediated by T lymphocytes of the cytotoxic/suppressor subset, as determined by cytofluorographic analysis and antibody plus complement-mediated lysis, using monoclonal antibodies to human lymphocyte surface antigen.

T lymphocyte-mediated cytotoxicity against autologous EBV-genome-bearing B cells

We have stimulated human peripheral blood lymphocytes in vitro with autologous EBV-infected or noninfected B cells. A cytotoxic response was obtained only when virally infected cells were used. The activity of the effector cells was restricted by the major histocompatibility complex and was directed against EBV-genome-bearing targets. The highest cytolytic response was obtained when lymphocytes of individuals previously exposed to the virus (EBV-VCA positive) were used. Lymphocytes of noninfected donors (EBV-VCA negative) gave a low response; the relative frequency of their effector cells was at least 4-fold lower. Lymphocytes of newborns did not respond. The cytotoxic activity was mediated by T lymphocytes of the cytotoxic/suppressor subset, as determined by cytofluorographic analysis and antibody plus complement-mediated lysis, using monoclonal antibodies to human lymphocyte surface antigen.

Age-associated changes in Epstein-Barr virus-induced human lymphocyte autoantibody responses

In the present investigation we have studied the capacity of the Epstein-Barr virus (EBV), a ubiquitous human B lymphocyte polyclonal activator, to induce cultured peripheral blood lymphocytes from umbilical cords, young adults (20 to 40 yr old), and elderly adults (75 to 90 yr old) to form IgM antibodies to human IgG or human thyroglobulin. The EBV preparation used was shown to exert its B cell stimulatory effect independently of T cell-suppressor effects. The cultures were studied in limiting dilution analyses, and the data were taken to represent relative numbers of B cell precursors of autoantibody-forming cells in the 3 age groups. The results showed: 1) the EBV-inducible IgM anti-IgG and anti-thyroglobulin-producing cells increased in number from birth to old age; 2) the rise occurred at different times of life for the 2 autoantibodies, anti-IgG reactive B cells increasing between birth and young adulthood, and anti-thyroglobulin reactive B cells between young adulthood and old age; 3) the apparent relative avidity of the anti-IgG for antigen was higher in the elderly adults than in the younger adults. We believe these findings are determined by differences in the frequencies of the respective self-reactive B cells in the circulation. What physiologic or environmental factors determine the differential expansions of the human autoreactive B lymphocytes for IgG and thyroglobulin are not known. It seems possible that individual variations in the sizes of these pools may be a factor in determining susceptibility to autoimmune disease.

Age-associated changes in Epstein-Barr virus-induced human lymphocyte autoantibody responses

In the present investigation we have studied the capacity of the Epstein-Barr virus (EBV), a ubiquitous human B lymphocyte polyclonal activator, to induce cultured peripheral blood lymphocytes from umbilical cords, young adults (20 to 40 yr old), and elderly adults (75 to 90 yr old) to form IgM antibodies to human IgG or human thyroglobulin. The EBV preparation used was shown to exert its B cell stimulatory effect independently of T cell-suppressor effects. The cultures were studied in limiting dilution analyses, and the data were taken to represent relative numbers of B cell precursors of autoantibody-forming cells in the 3 age groups. The results showed: 1) the EBV-inducible IgM anti-IgG and anti-thyroglobulin-producing cells increased in number from birth to old age; 2) the rise occurred at different times of life for the 2 autoantibodies, anti-IgG reactive B cells increasing between birth and young adulthood, and anti-thyroglobulin reactive B cells between young adulthood and old age; 3) the apparent relative avidity of the anti-IgG for antigen was higher in the elderly adults than in the younger adults. We believe these findings are determined by differences in the frequencies of the respective self-reactive B cells in the circulation. What physiologic or environmental factors determine the differential expansions of the human autoreactive B lymphocytes for IgG and thyroglobulin are not known. It seems possible that individual variations in the sizes of these pools may be a factor in determining susceptibility to autoimmune disease.

Inheritance of immunoglobulin M rheumatoid-factor idiotypes

The idiotypic determinants on IgM rheumatoid factor (RF) from a single family have been analyzed. Rabbit Fab'2 antiidiotypic antibody was prepared against purified IgM-RF from a patient with rheumatoid arthritis. As measured by radioimmunoassay, the antiidiotype reacted with at least 90% of the patient's RF, but not with non-RF immunoglobulins from the same serum, nor with 10 of 11 polyclonal and monoclonal RF from unrelated individuals. Cross-reacting idiotypes were detected on RF in four of the patients' first degree relatives, spanning three generations, without apparent relation of HLA type or clinical rheumatoid arthritis. These results suggest that IgM-RF associated idiotypes were inherited in this family.

Validation of conditions for efficient detection of HPRT and APRT mutations in suspension-cultured Chinese hamster ovary cells

Conditions for reliable and efficient assay of mutations affecting the activity of HPRT (hypoxanthine phosphoribosyltransferase EC 2.4.2.8) and APRT (adenine phosphoribosyltransferase EC 2.4.2.7) have been determined for a strain of CHO (Chinese hamster ovary) cells that has been adapted for rapid growth both in suspension culture and in monolayer. To facilitate measurement of mutation at the aprt locus, clones were derived that are presumptively heterozygous at that locus. At a limiting concentration of 8 microgram/ml of azaadenine, 14/16 of the resistant clones picked and tested had approximately 1/2 of the APRT activity of the wild-type cells. One such clone, strain AA8, was chosen for further studies and found to be readily mutable to resistance to 80 microgram/ml azaadenine. Most of the highly resistant colonies isolated (21/24) had very low in vitro APRT activity. The optimal conditions for detection of TGr and AAr mutations were determined for two critical parameters, expression time and cell density. Cultures treated with mutagen either in monolayer or in suspension were allowed to express mutations in suspension. The expression of mutations induced by UV light, EMS, and ICR-191 was complete by 3 days for AAr and by 4-5 days for TGr. The time required to reach a maximal frequency of mutants was essentially independent of the type of mutagen and the level of survival after treatment. Induced mutation frequencies for both loci were notably stable during the time intervals examined. With respect to cell-density conditions, both markers were detected at frequencies that were independent of the cell inocula over the range of 1 x 10(5) to 1 x 10(6) cells per 100-mm petri dish (i.e. 1.6 x 10(3) to 1.6 x 10(4) cells/cm2) containing 20 ml of medium. These results were obtained with both mutagenized populations and with reconstructed mixtures obtained by adding drug-resistant cells to varying numbers of wild-type cells. The rapid expression of mutations for both markers, particularly AAr, combined with the advantage that large inocula can be plated for selection of mutants, make this CHO strain an attractive system for the simultaneous measurement of mutations at the autosomal aprt and X-linked hprt loci.

DNA crosslinking, sister-chromatid exchange and specific-locus mutations

Chinese hamster ovary cells were treated with the DNA-crosslinking chemicals, mitomycin C (MMC) and porfiromycin (POR), and their monofunctional derivative decarbamoyl mitomycin C (DCMMC). After exposure, the cells were studied for the induction of sister-chromatid exchanges (SCEs) and mutations at the hypoxanthine phosphoribosyltransferase and adenine phosphoribosyltransferase loci. The frequency of SCEs varied significantly in successive sampling intervals, requiring the weighting of each interval by the percentage of second-division mitosis in that interval to obtain the mean SCE frequency for each dose. All 3 compounds were potent inducers of SCEs but weakly mutagenic. All 3 chemicals by concentration were approximately equally effective in inducing SCEs or mutations. When the induced SCEs and mutations were compared at equal levels of survival, DCMMC was slightly more effective than MMC or POR in inducing SCEs and somewhat less mutagenic. These results indicate that the DNA interstrand crosslink is not the major lesion responsible for the induction of SCE or mutation by these compounds.

113mIn-tripolyphosphate: a new radiopharmaceutical for bone scanning

A compound was synthetized, which by X-Ray diffraction studies proved to be hexahydrated sodium tripolyphosphate. By means of in vitro procedures, it was demonstrated that this compound was able to complex trivalent cations, and that 113mIn could be completely incorporated to it. In vivo studies in rats, and scans performed with this new radiopharmaceutical in humans showed its highly selective accumulation in metastasic bone tumors.

Macrophage-T cell interaction mediated by immunogenic and non-immunogenic forms of a monofunctional antigen

As an approach to the elucidation of the essential steps in the immune pathway, the uptake and retention of immunogenic and non-immunogenic analogs of a monofunctional antigen by guinea pig macrophages and the efficiency of macrophages pulsed with the compounds to present antigen to sensitized T lymphocytes were compared. L-Tyrosine-azobenzene-p-arsonate (RAT) and its non-immunogenic analog, 4-hydroxyphenyl-n-propane-3-azobenzene-p-arsonate (RAN), react similarly with antiarsonate antibody, but RAN, unlike RAT, is unable to induce cellular immunity in guinea pigs. The uptake and retention patterns of the two compounds by macrophages differed in that, at a given time, more RAN than RAT was retained and detectable on cell surfaces by anti-arsonate antibody. Equivalent numbers of T lymphocytes from guinea pigs sensitized to RAT formed antigen-dependent clusters with macrophages pulsed with either RAT or RAN after 24 hr in culture, but not with macrophages pulsed with an azobenzenoid compound of unrelated specificity. On the other hand, T lymphocytes from guinea pigs immunized with RAN showed no significant capacity to bind to macrophages which had been pulsed with any of the compounds. The number of lymphocytes from RAT-sensitized animals which bound to RAT-pulsed macrophages remained relatively stable over a 48 hr period, whereas clusters of the same lymphocytes with RAN-pulsed macrophages dissocitated to background levels within that time. Early cluster formation mediated by RAN, as well as its ability to induce transient specific T cell unresponsiveness to RAT in vivo, indicate that T cells are capable of recognizing (binding) the non-immunogen. However, such early, and perhaps weak, interaction with RAN-pulsed macrophages did not induce DNA synthesis by T cells. Anti-Ia serum completely blocked cluster formation mediated by either RAT or RAN. Thus, the only significant distinction disclosed by these studies between the immunogenic and non-immunogenic compounds was the stability of macrophage-T cell interaction as determined by the persistence of antigen mediated cell clusters in culture, suggesting that this may be a factor in immunogenic discrimination.

Spatial requirements between haptenic and carrier determinants for T-dependent antibody responses

To gauge the proximity between cooperating T and B cells required for effective triggering of antibody production, guinea pigs were immunized with bifunctional antigens in which the haptenic and carrier determinants were separated by rigid spacers of varied dimension. These took the form 2,4-dinitrophenol-(proline)n-L-tyrosine-p-azobenzenearsonate, where n varied from 1 to 40 proline residues. Animals immunized with n = 10 and n = 22 compounds made strong anti-DNP antibody responses, whereas animals immunized with bifunctional compounds containing longer spacers did not make antibody detectable by precipitation. It can be calculated on the basis of very strong physicochemical evidence for the rigidity and axial translation of poly-L-proline chains in solution that the cut-off point for effective interaction between T and B cells lies between 69 and 97 A U.

T-lymphocyte activation by immunogenic determinants

Synthetic antigens have been of great value in elucidating the relationships between antigen structure and lymphocyte activation. The compound RAT behaves as a monofunctional antigen in guinea pigs and mice, inducing T-lymphocyte responses without appreciable circulating antibody, although the ABA-specific B cell population is expanded by immunization with the monovalent molecule. On the other hand, bifunctional antigens composed of one RAT moiety serving as a carrier and a second chemical group, either identical to or different from RAT, serving as a hapten, induced antibody responses. In such responses, T cell specificity was always directed against the RAT component. Using symmetrical bifunctional antigens with rigid or flexible spacers between the two determinants, marked differences in structural requirements for cell triggering, assessed by antigen-induced lymphocyte proliferation, and for cell cooperation, determined by antibody formation, were found. Rigidly spaced bifunctional antigens serve admirably for cooperation but poorly for T cell activation, underscoring the advantage of two-point binding for the latter.

Immunity to lymphoid tumors in syngeneic mice by immunization with mitomycin C-treated cells

Immunization of mice with syngeneic mitomycin C-treated lymphoid tumor cells (EL-4 and S49A) conferred a high degree of immunity to transplantation with viable tumor cells in syngeneic animals. The development of this immunity was paralleled by the development of specific cell-mediated cytotoxicity; no anti-tumor antibodies could be detected in the immunized animals. In contrast to the high immunoprophylactic capacity of mitomycin C-treated cells, attempts to utilize these cells for immunotherapy were unsuccessful. Preliminary experiments did not reveal antigenic differences between mitomycin C-treated and untreated tumor cells.

Active and Inactive States of Immunologic Unresponsiveness

Immunologic tolerance was induced in newborn mice by administration of 1, 5, 10, or 20 mg of lysozyme. These mice were subsequently challenged with a mixture of lysozyme and bovine serum albumin (BSA), or with a covalently coupled conjugate of lysozyme and succinylated BSA. When challenged at 6 weeks of age none of these mice responded to lysozyme when administered admixed with BSA. Of the mice challenged with the lysozyme-SBSA conjugate, those tolerized with 1 or 5 mg of lysozyme responded with antilysozyme antibodies but those tolerized with 10 or 20 mg of lysozyme did not. When challenged at 10 weeks of age, mice which had been tolerized with 20 mg of lysozyme mounted a low level antilysozyme response to both the mixture and the conjugate. Assessment of the response of these animals to BSA and SBSA revealed that the anti-SBSA responses of the conjugate-challenged animals were significantly suppressed whereas the anti-BSA response of the mixture-challenged animals was unaffected.

Tolerance was also induced in adult mice, by the injection of 20, 50, or 100 mg of lysozyme. When challenged 12 days after cessation of the tolerizing regimen, all of these mice exhibited suppressed antilysozyme responses regardless of the challenge antigen, although the antilysozyme responses to the conjugate were slightly higher than to the mixture. No suppression of either anti-BSA or anti-SBSA responsiveness was seen in any of these adult tolerant animals.

It was concluded that administration of low doses of tolerogen to neonatal mice results in only T cell tolerance whereas administration of higher doses of tolerogen also effects B cell responsiveness. Furthermore, neonatally induced tolerance appeared to involve some form of active suppression which did not appear to be a factor in the adult tolerized mice. This suppression was only demonstrable at the B cell level.