Increased T gamma and T mu cells in BALB/c mice with IgG and IgM plasmacytomas and hybridomas

The results of previous studies in our laboratory have shown that mice bearing plasmacytomas and hybridomas that secrete IgA or IgE are accompanied by increased frequencies of Lyt-1-2+ T lymphocytes bearing Fc receptors (FcR) for IgA (T alpha) or IgE (T epsilon), respectively. The present study was undertaken to examine whether IgG- or IgM-secreting tumors influenced the frequency of T lymphocytes that express FcR for IgG or IgM. We studied mice bearing IgG- and IgM-secreting plasmacytomas and hybridomas. BALB/c mice injected subcutaneously with the IgG-secreting hybridoma HDP1 (gamma 1 kappa, anti-TNP) were sequentially examined for the frequencies and Lyt phenotypes of splenic lymphocytes bearing FcR for IgG (T gamma), IgM (T mu), and IgA (T alpha). A threefold increase in the frequency of T gamma lymphocytes that were Lyt-1-2+, L3T4- was seen. The frequencies of T mu and T alpha lymphocytes in these mice were not significantly altered. Similarly, mice injected subcutaneously with the IgM-secreting plasmacytoma MOPC 104E (mu lambda, anti-dextran) or the IgM-secreting hybridoma C1D1 (mu kappa, anti-ox RBC) were examined sequentially for the frequencies of T gamma, T mu, and T alpha lymphocytes. Mice with established IgM subcutaneous tumors showed a twofold increase in splenic, nylon wool-nonadherent T mu lymphocytes. This was associated with a relative increase in Lyt-2+ splenic T lymphocytes and a relative decrease in Lyt-1+ splenic T lymphocytes. No changes were observed in the frequencies of either T gamma or T alpha lymphocytes. These studies extend to IgG and IgM the observation that plasmacytomas and hybridomas secreting immunoglobulins of a specific isotype cause an expansion of T lymphocytes bearing FcR specific for the corresponding isotype. The expansion of FcR+ Lyt-1-2+ T lymphocytes likely represents an exaggerated, but otherwise normal, immunoregulatory response of the host. These cells may be an important element in the regulation of isotype expression.     

Lyt-2+ T cell-mediated protection against listeriosis. Protection correlates with phagocyte depletion but not with IFN-gamma production

The transfer of listeria-immune splenocytes into non-immune mice markedly increases host resistance to listeriosis. To study the mechanism for this enhancement, we compared the inflammatory response to infection in nonimmune and adoptively immunized mice. Despite much better containment of bacterial growth, adoptively immunized animals accumulated significantly fewer phagocytes (neutrophils and macrophages) in the spleen and liver than controls. Immune T cells not only inhibited phagocyte accumulation but also reduced the in vitro anti-listerial activity of splenocytes. Significant differences in phagocyte accumulation were observed even when the initial listeria dose was adjusted to produce comparable spleen listeria loads in immune and non-immune animals. However, bone marrow and peripheral blood phagocyte counts were similar in both groups. Depletion of Lyt-2+ cells (using mAb and C) from donor splenocytes prevented the transfer of protection and increased phagocyte accumulation without altering listeria-dependent IFN-gamma production by donor or recipient splenocytes in vitro. L3T4 depletion did not affect host resistance or phagocyte accumulation even though it reduced in vitro interferon production by donor cells. Hence the different effects of L3T4+ and Lyt-2+ cells in vivo cannot be explained simply by variations in IFN production. We suggest this paradoxical suppression of phagocyte accumulation during adoptive transfer may reflect lysis of bacteria-laden phagocytes by listeria-specific Lyt-2+ cells in vivo. Selective destruction of older, heavily infected cells might contribute to host resistance by eliminating a potential site for intracellular proliferation of bacteria.     

A murine plasmacytoma MOPC 104E resistant to cyclophosphamide is resistant to immunotherapy

Summary A murine plasmacytoma MOPC 104E (MOPC) is highly sensitive to chemotherapeutic agents such as cyclophosphamide and mitomycin C as well as to immunotherapy (OK-432-combined adoptive immunotherapy using interleukin-2-cultured killer cells). In the present study, we prepared cyclophosphamide-resistant MOPC cells (MOPC-CPA/R) by serial in vivo passage of tumor cells following cyclophosphamide treatment. The in vivo sensitivity of MOPC-CPA/R to mitomycin C or to immunotherapy (OK-432-combined adoptive immunotherapy) was significantly decreased compared to the parent MOPC. In vitro experiments showed that MOPC-CPA/R were more resistant (five-fold) to lysis by cultured immune spleen cells than MOPC. Inhibition of the lytic activity of cultured immune spleen cells against MOPC was significantly increased (P <0.05) by the addition of unlabeled MOPC compared to unlabeled MOPC-CPA/R. These results suggest that MOPC-CPA/R express weaker antigenicity than MOPC. However, the transfer of immune spleen cells cultured with tumor extract derived from MOPC-CPA/R significantly prolonged the survival of MOPC-CPA/R-inoculated mice. Thus, by repeated cyclophosphamide treatment, tumor cells with low-antigenicity were selected. These tumor cells had lower sensitivity to another chemotherapeutic agent and immunotherapy. Such an immunological response may play an important role in cancer therapy.     

Tumor immunity directed against MOPC 104E: Effect of various therapeutic regimens

Summary Animals bearing the passable plasmacytoma MOPC 104E could be cured of palpable tumors (0.6–2.0×10⁸ cells) with single 10–250 mg/kg doses of cyclophosphamide or single localized x-ray doses greater than 1600 R. Residual tumor immunity of cured animals was determined by their ability to reject graded numbers of viable MOPC 104E cells 30 days following curative therapy. High doses of cyclophosphamide (250 mg/kg), although curative, left significantly less residual tumor immunity than either low dose cyclophosphamide (10 mg/kg) or localized irradiation. Animals cured of palpable tumors by high doses of cyclophosphamide nonetheless rejected greater numbers of cells in secondary challenge than did untreated control animals.This investigation received support from NIH Grants 13371, 17065, 05136, and 09082 from the National Cancer InstituteSubmitted in partial fulfilment of the degree Doctor of Philosophy in Radiation Biology     

Enlargement of Lyt-2-positive T cells is associated with functional impairment and autoimmune hemolytic anemia in New Zealand Black mice

We investigated the relationship between the increased cell diameter of Lyt-2+ T cells and the development of autoimmune disease in aging NZB and NZB X NZW F1 hybrid (BW) mice. Individual animals were analyzed for Lyt-2+ T cell size (by narrow-angle forward light scatter), anti-erythrocyte autoantibodies, anemia, proteinuria, and splenomegaly. The peak light scatter of the Lyt-2+ T cells correlated with the level of anti-erythrocyte autoantibodies and severity of hemolytic anemia, but not with proteinuria or splenomegaly. The cell size of this T cell subset did not increase in old BW or in NZB mice homozygous for the xid gene (NZB.xid). The in vivo administration of bacterial lipopolysaccharide to young NZB mice did not stimulate the enlargement of Lyt-2+ T cells. Ly-2+ T cells from old NZB mice could be stimulated by concanavalin A (Con A) to express interleukin 2 (IL 2) receptors and to synthesize DNA in vitro. However, in vivo administration of Con A to old NZB mice did not induce the expression of IL 2 receptors on Lyt-2+ T cells. Further, in vivo T suppressor function was impaired in old NZB mice with enlarged Lyt-2+ T cells. Thus, the enlargement of Lyt-2+ T cells in old NZB mice appears related to impaired T cell function in vivo and is associated with the development of anti-erythrocyte autoantibodies and autoimmune hemolytic anemia.     

Cellular subsets involved in cell-mediated immunity to murine Plasmodium yoelii 17X malaria

Cell mediated immunity to nonlethal Plasmodium yoelli 17X (PY17X-NL) was examined in the CBA/CaJ mouse by adoptive transfer of sensitized T lymphocyte subsets. In intact mice, PY17X-NL causes a self-limiting infection with parasitemia levels ranging from 10 to 25% of total red blood cells. Upon recovery, mice are refractory to subsequent challenge with the homologous parasite. In T cell-depleted mice, PY17X-NL infections are extremely virulent and result in death of the host after parasitemia levels reach 50% or higher. The transfer of either Lyt-1 T cells or Lyt-2 T cells from immune animals into normal, naive animals produced accelerated recovery to subsequent infection. However, this adoptive transfer of immunity by either subset was dependent upon the presence of an I-J+, Lyt-null cell in the immune population. T cell deprivation precluded the ability of animals to control blood-stage infections. When T cell-depleted mice were reconstituted with naive, Ig-negative (T cell-enriched) spleen cells, parasitemia levels were controlled and the parasites were eliminated. When T cell-deprived animals were reconstituted with naive Lyt-1+2-, Ig-negative spleen cells, they experienced twofold higher parasitemias of longer duration than mice receiving unfractionated cells. Two of six of these Lyt-1 mice died of fulminant infections, suggesting that the presence of naive Lyt-2 cells enhances the degree of protection. Immune Lyt-2 T cells were highly protective in T cell-depleted animals. Protection by sensitized Lyt-1 T cells correlated with the induction of a monocytosis. On the other hand, protection by Lyt-2T cells occurred in the absence of monocytosis. The possibility that the immunity induced by each T cell subset is mediated by a different effector mechanism is discussed.     

Capacity of purified unprimed Lyt-2+ cells to reject Ia- H-2-different tumor cells in the Winn assay

To examine which cells participate in primary anti-H-2 responses to Ia- tumors in vivo, irradiated mice were injected intracutaneously with small doses of tumor cells mixed with purified populations of host-type lymphoid cells. Studies with three different Ia- H-2-different tumors showed that purified unprimed Lyt-2+ cells were highly efficient at suppressing tumor growth. Lyt-2+ cells were appreciably more effective at suppressing tumor growth than unseparated T cells, and no protection was seen with injection of L3T4+ cells (except in the late states of tumor growth). It is suggested that class I alloantigens on the tumors are directly immunogenic for Lyt-2+ cells. Without need for help from L3T4+ cells, the responding Lyt-2+ cells rapidly differentiate into cytotoxic cells and destroy the tumor cells before macroscopic tumors can arise.     

Antitumor and therapeutic effects of spleen cells from tumor-bearing mice cultured with T cell growth factor and soluble tumor extract

Summary Spleen cells of BALB/c mice that had been inoculated with syngeneic plasmacytoma MOPC 104E were cultured for 11 days in T-cell growth factor (TCGF) and ultrasonicated tumor extract (USE). Cultured lymphocytes (MOPC-CL) possessed three-fold more lytic units than normal spleen cells cultured in TCGF without USE (N-CL). Moreover, the in vivo neutralization assay suggested that MOPC-CL were composed of at least two populations, one possessing tumor-specific and the other nonspecific antitumor activity. When 2×10⁷ of MOPC-CL were administered IP to mice that had been inoculated IP with 10⁵ MOPC 104E cells 5 days previously marginal prolongation of survival was observed. This effect was not augmented by the single injection of a larger number (5×10⁷) of CL, but was augmented by the repeated daily administration for 4 days (from day 5 to day 8 after the inoculation) of the same total number (5×10⁷) of CL. In addition, IP injection of the streptococcal preparation OK432 before the transfer of CL significantly enhanced the therapeutic efficacy, and resulted in a cure rate of 20%. The mechanism of this combined effect appears to involve the effect of OK432 on interleukin 2 (IL-2) regulation systems in vivo. Our culture system with TCGF and USE and our therapy system with OK432 and CL allow the clinical application of adoptive immunotherapy for the many types of solid cancers.     

Regulation of Ia+ reticulum cell sarcoma (RCS) growth in syngeneic SJL/J mice. I. Inhibition of tumor growth by passive administration of L3T4 monoclonal antibody before or after tumor inoculation

Spontaneously arising reticulum cell sarcoma (RCS) tumors in SJL/J mice stimulate syngeneic host T lymphocytes to proliferate and are dependent on host T cells for maintenance and growth. Tumor-associated Ia antigens have been implicated in the proliferative response both in vivo and in vitro, and the responding T cells are predominantly Lyt-1+2- L3T4+. We hypothesized that elimination or depletion of the responding L3T4 subpopulation in vivo should inhibit growth of transplantable RCS tumors, and continued RCS growth may be dependent on the continued presence of L3T4 cells. This hypothesis was tested experimentally by examining the effect of passive administration of L3T4 monoclonal antibody (mAb) into SJL/J mice either before or at different times after tumor inoculation. The tumor inoculum used killed all mice 15 to 30 days after injection. Administration of a single dose of L3T4 mAb 4 days before tumor inoculation resulted in complete depletion of L3T4 cells and complete inhibition of tumor growth. The antibody-treated mice survived with no sign of tumor growth even after complete recovery of L3T4+ cells. These results demonstrate that initiation of tumor growth is dependent on host L3T4+ cells. Administration of mAb as late as 7 days after tumor inoculation resulted in inhibition of tumor growth, and administration of mAb at day 10 resulted in significant inhibition of tumor growth. Compared with the kinetics of tumor growth in normal control mice, administration of L3T4 after tumor inoculation results in tumor growth arrest. These findings demonstrate that continued tumor growth in vivo is dependent on the presence of L3T4+ cells. In the RCS system, the present studies show that administration of mAb to L3T4+ cells is therapeutic in that it inhibits the induction of tumor growth, and it also prevents tumor growth in tumor-bearing animals.     

The role of tumor-specific Lyt-1+2- T cells in eradicating tumor cells in vivo. I. Lyt-1+2- T cells do not necessarily require recruitment of host's cytotoxic T cell precursors for implementation of in vivo immunity

The present study determines the Ly phenotype of T cells mediating tumor cell rejection in vivo and investigates some of cellular mechanisms involved in the in vivo protective immunity. C3H/HeN mice were immunized to syngeneic X5563 plasmacytoma by intradermal (i.d.) inoculation of viable X5563 tumor cells, followed by the surgical resection of the tumor. Spleen cells from these immune mice were fractionated by treatment with anti-Lyt antibodies plus complement, and each Lyt subpopulation was tested for the reconstituting potential of in vivo protective immunity in syngeneic T cell-depleted mice (B cell mice). When C3H/HeN B cell mice were adoptively transferred with Lyt-1-2+ T cells from the above tumor-immunized mice, these B cell mice exhibited an appreciable cytotoxic T lymphocyte (CTL) response to the X5563 tumor, whereas they failed to resist the i.d. challenge of X5563 tumor cells. In contrast, the adoptive transfer of Lyt-1+2- anti-X5563 immune T cells into B cell mice produced complete protection against the subsequent tumor cell challenge. Although no CTL or antibody response against X5563 tumors was detected in the above tumor-resistant B cell mice, these mice were able to retain Lyt-1+2- T cell-mediated delayed-type hypersensitivity (DTH) responses to the X5563 tumor. These results indicate that Lyt-1+2- T cells depleted of the Lyt-2+ T cell subpopulation containing CTL or CTL precursors are effective in in vivo protective immunity, and that these Lyt-1+2- T cells implement their in vivo anti-tumor activity without inducing CTL or antibody responses. The mechanism(s) by which Lyt-1+2- T cells function in vivo for the implementation of tumor-specific immunity is discussed in the context of DTH responses to the tumor-associated antigens and its related Lyt-1+2- T cell-mediated lymphokine production.     

Untranslated immunoglobulin kappa light chain mRNA in a lambda light chain-producing mouse myeloma, MOPC104E

Fourteen clones were isolated in culture from a mouse myeloma, MOPC104E. All clones had kappa and lambda types of light chain mRNAs in approximately equimolar quantity as assayed by hybridization with specific complementary DNA (cDNA). However, the myeloma produces and secretes only lambda-type light chain protein. Both kappa- and lambda-type mRNAs in these clones were indistinguishable from kappa- and lambda-type mRNAs of other myelomas with respect to (a) adsorption to oligo-(dT) cellulose, (b) molecular size (12.6 S), and (c) thermal stability of the hybrids formed with corresponding cDNA. The kappa chain mRNA of MOPC104E cells, however, was translated very inefficiently both in vivo and in vitro, whereas the lambda chain mRNA was translated efficiently. These results indicate that each cell of MOPC104E myeloma synthesizes a crippled kappa chain mRNA in addition to a normal lambda chain mRNA.     

T cells subsets responsible for clearance of Sendai virus from infected mouse lungs

T cell subsets responsible for clearance of Sendai virus from mouse lungs determined by adoptive transfer of immune spleen cell fractions to infected nude mice. T cells with antiviral activity developed in spleens by 7 days after intranasal infection. Spleen cell fractions depleted of Lyt-2+, Lyt-1+, or L3T4+ cells showed antiviral activity in vivo, although the degree of the activity was lower than that of control whole spleen cells. The antiviral activity of the Lyt-2+ cell-depleted fraction was consistently higher than that of L3T4+ (Lyt-1+)-depleted cells. In vitro cytotoxic activity against Sendai virus-associated, syngeneic lipopolysaccharide-blast cells was detected in stimulated cells from intraperitoneally immunized mice but was lost after depletion of Lyt-2+ cells. Multiple injection of anti-Sendai virus antibody into infected nude mice had no effect on lung virus titer. These results indicate that L3T4+ (Lyt-1+) and Lyt-2+ subsets are cooperatively responsible for efficient clearance of Sendai virus from the mouse lung.     

Impact of genetically regulated T cell proliferation on acquired resistance to Listeria monocytogenes

Two lines of mice genetically selected for high and low in vitro responses to PHA were used to evaluate the impact of T cell polyclonal expansion on acquired resistance to Listeria monocytogenes. The selective breeding induced two major consequences in low responder mice: (1) a reduction of the number of L3T4+ cells and (2) a restriction of T cell expansion upon PHA stimulation, predominantly affecting the Lyt-2+ subset, and associated with an abridgment of IL-2 production. In vivo PHA stimulation induced anti-Listeria protection in high responder mice, but was much less effective in low responder mice. Flow cytometer analysis revealed that T cell proliferation was also reduced in low responder mice during the course of Listeria infection, implying both L3T4+ and Lyt-2+ subsets. This defect did not apparently influence the kinetics of bacterial elimination in host tissues, which was similar in both lines during primary Listeria infection. In contrast, the expression of delayed-type hypersensitivity to Listeria antigens and the level of immunologic memory were significantly reduced in low responder mice. In vivo selective T cell depletion by anti-L3T4 or anti-Lyt-2 mAb allowed us to demonstrate the predominant role of Lyt-2+ cells in protection and that of L3T4+ cells in the expression of delayed-type hypersensitivity.     

T-helper-cell-specific monoclonal antibody inhibits growth of B-cell lymphomas in syngeneic SJL/J mice

Transplantable follicular center cell lymphomas of SJL/J mice are B-cell tumors that stimulate proliferation of host T-helper (TH) cells and which grow progressively in the peripheral lymphoid tissues of immunocompetent recipients. However, tumor growth is compromised in immunosuppressed syngeneic recipients, suggesting that the host response to SJL follicular center cell (SJL/FCC) lymphoma cells is required for optimal tumor growth. In vitro studies indicate that the host TH cells (Lyt-1+, 2-, L3T4a+) which respond to the major histocompatibility complex (MHC) class II (I-As) surface determinants on the SJL/FCC lymphoma cells produce a variety of lymphokines, some of which may promote tumor growth in vivo. The results of this study demonstrate that treatment of lymphoma-injected mice with L3T4a-specific mAb inhibits the growth of the SJL/FCC lymphoma cells, despite the fact that these tumor cells do not express L3T4a determinants. Thus, in this model, mAb therapy targeting host immune cells rather than the tumor cells is an effective means to control tumor growth. Long-term observation of SJL/FCC lymphoma-injected, anti-L3T4a mAb-treated mice reveals prolonged survival of the majority of these animals with periodic recurrence of tumor growth. During periods of remission, LN cells from these long-term surviving animals were unable to mount the characteristic in vitro host response to irradiated SJL/FCC lymphoma cells. These results provide direct evidence that SJL/FCC lymphoma cells fail to retain their characteristic neoplastic properties in a microenvironment that is initially devoid of tumor-responsive TH cells.     

Effector phenotypes and mechanisms of antitumor immune reactivity of tumor-immunized and tumor-bearing mice in two syngeneic tumors.

By using two different syngeneic tumors, Meth A sarcoma and RL male 1 lymphoma of BALB/c origin, the present study was designed to investigate the subset(s) of T cells mediating in vivo antitumor immune responses and some of the effector mechanisms of in vivo protective immunity in BALB/c mice immunized against tumor or bearing tumor. Spleen cells from the mice immunized against Meth A tumor or bearing Meth A tumor inhibited the growth of Meth A tumor in the Winn assay. In the Meth A-immunized mice, L3T4+ (CD4+) cells played a major role in mediating the inhibitory activity against Meth A tumor growth, whereas in the Meth A-bearing mice, the antitumor protective immunity was mediated by both L3T4+ and Lyt-2+ (CD8+) cells. Spleen cells from the Meth A-immunized or Meth A-bearing mice were not able to generate cytotoxic T lymphocytes (CTL) directed against Meth A tumor after the in vitro restimulation of spleen cells with mitomycin C (MMC)-treated Meth A cells, while fresh spleen cells from the Meth A-immunized or Meth A-bearing mice were able to induce the strong delayed-type hypersensitivity (DTH) responses to Meth A tumor. The DTH response to Meth A tumor was mediated by L3T4+ cells in the Meth A-immunized mice and by both L3T4+ and Lyt-2+ cells in the Meth A-bearing mice. In the similar experiments performed in the RL male 1 lymphoma, the antitumor activity in spleen cells from the RL male 1-immunized or RL male 1-bearing mice depended on Lyt-2+ but not L3T4+ cells in the Winn assay. When spleen cells from the RL male 1-immunized or RL male 1-bearing mice were cultured with MMC-treated RL male 1 cells for 5 days, an appreciable CTL response to RL male 1 tumor was induced. These results suggest that the nature of tumor and/or tumor antigens determines which T cell subset is required to exhibit the protective immunity against tumor and thus the different effector mechanisms could be induced in the different tumor models. Furthermore, these data support the conclusion that antitumor T cell responses are affected by the immune state of host to tumor.     

Cellular interactions and the role of interleukin 2 in the expression and induction of immunity against a syngeneic murine sarcoma

We have previously demonstrated that following the adoptive transfer of immune cells, the regression of established pulmonary metastases from a weakly immunogenic sarcoma, MCA 105, required the collaboration of two T cell subsets. In this study, we found that the critical role played by L3T4+ immune cells was to provide a helper function since tumor regression proceeded in the absence of L3T4+ immune cells if exogenous interleukin 2 (IL-2) was administered. To extend these observations, we analyzed the events leading to the induction and generation of L3T4+ and Lyt-2+ immune T cells after immunization of mice with viable tumor cells admixed with Corynebacterium parvum. The basic protocol involved immunization, surgical excision of the immunization site on day 7, and challenge with viable tumor cells on day 21. The ability of mice to reject tumor challenge provided a means to evaluate the occurrence of a systemic antitumor immunity. With the use of this experimental protocol, we have found that depletion of T cell subsets in vivo with either L3T4 or Lyt-2 monoclonal antibodies after active immunization abrogated the development of antitumor immunity. Mice immunized and depleted of L3T4+ but not Lyt-2+ T cells were able to reject tumor challenge if exogenous IL-2 was given for 7 days. However, the rejection of tumor challenge required 3 days of additional exogenous IL-2 administration. These results indicate that the induction of Lyt-2+ immune T cells depended on the helper function of L3T4+ T cells via the secretion of IL-2. In the absence of L3T4+ immune lymphocytes, the expression of antitumor immunity by Lyt-2+ immune cells could be facilitated by in vivo administration of exogenous IL-2. The induction of L3T4+ immune T cells, on the other hand, occurred independently of the Lyt-2+ T cell response because the transfer of spleen cells from Lyt-2+ cell-depleted, immunized animals was able to restore antitumor reactivity in L3T4+ cell-depleted, immunized mice. These results demonstrate the intricate cellular interactions leading to the induction as well as the expression of antitumor immunity.     

Immunotherapy of lymphoid and nonlymphoid tumors with monoclonal anti-Lyt-1 antibodies

Monoclonal antibodies against the T cell differentiation antigen Lyt-1 were effective in the therapy of transplanted mouse tumors. A possible mechanism whereby anti-Lyt-1 antibodies directly bind and affect the tumor cells was excluded by the following findings: a) growth of lymphoid and nonlymphoid tumors (which lack Lyt-1 antigen) was affected by anti-Lyt-1 antibodies; and b) the curative effect of passively administered anti-Lyt-1 anti-bodies was abrogated in mice depleted of T cells, supporting a mechanism whereby host Lyt-1+ cells were involved in tumor therapy. Treatment with anti-Lyt-1 antibodies was not accompanied by depletion of Lyt-1+ cells from lymphoid organs, indicating that the administered antibodies altered Lyt-1+ cell functions without affecting their frequency. In view of the in vitro enhancing effects of anti-Lyt-1 antibodies on a variety of immune responses (including lymphokine secretion and generation of cytotoxic T cell), it is suggested that the potentiation of Lyt-1+ cell activity by passively administered anti-Lyt-1 antibodies results in tumor rejection.     

Evidence for idiotypic- and antiidiotypic B-B cellular interaction with the use of cloned antiidiotypic B cell line

Immunization of BALB/c mice with MOPC104E myeloma protein induces antiidiotypic B lymphocytes that have Id-specific enhancing activity on antibody production. The B-B cell interaction was restricted to both Igh and class II MHC. However, anti-Thy-1 and C-treated splenic B cells were maintained for more than 1 y in a mixture of Con A-stimulated splenocyte culture supernatant and synthetic medium. In applying the long term culture method, we have established a cloned B cell line named B19-1d, B19-1d cells are specific to MOPC104E or J558 cross-reactive Id and they express surface mu, lambda but no Ly-1. B19-1d do not spontaneously secrete Ig but produce them upon stimulation with bacterial LPS. The effect of B19-1d cell line on idiotypic antibody production was tested. Addition of only 10 to 100 B19-1d cells into dextran-immune B cell culture greatly enhanced the Id+ antidextran antibody responses. On the contrary, the antidextran antibody production was suppressed by the higher doses of B19-1d cells. The effective cooperation between dextran-immune B cells and B19-1d cloned B cells was restricted to class II MHC. The role of idiotypic- and antiidiotypic B-B cell interaction in immune regulation and repertoire generation was suggested.     

Interleukin-5 induces tumor suppression by peritoneal exudate cells in mice

The antitumor activity of peritoneal exudate cells (PEC) induced by murine interleukin-5 (mIL-5) was examined using Meth-A sarcoma cells transplanted into the peritoneal cavity of mice. Although in vitro treatment of Meth-A sarcoma cells with mIL-5 did not result in inhibition of their growth, treatment of mice intraperitoneally with mIL-5 (1 g/day) from day –5 to +5 (tumor cells were inoculated on day 0) led to a significant increase in survival or even rejection of tumor cells. This antitumor effect depended on the dose of mIL-5. Interestingly, there was identical therapeutic activity when the protocol of days –10 to –1 was used as opposed to –5 to +5. In addition, post-treatment with mIL-5 from day +1 to +10 was ineffective. This suggests that the therapeutic activity of IL-5 is largely prophylactic. Under the former condition, the number of PEC was found to increase over 50-fold when compared to levels in control mice. Moreover, the antitumor effect of mIL-5 was completely abolished by subcutaneous injection of anti-mIL-5 monoclonal antibodies. The treatment of mice injected intraperitoneally with human IL-2 also resulted in an increase in survival. Winn assay experiments using PEC recovered from mIL-5-treated mice (1g/day, from day –10 to –1) revealed that these PEC could mediate antitumor activity against Meth-A sarcoma cells. Furthermore, when the cured mice were re-injected with Meth-A sarcoma cells or syngeneic MOPC 104E cells, they could reject Meth-A sarcoma cells but not MOPC 104E cells, indicating that immune memory had been generated. These results suggest that IL-5 augumented the PEC tumoricidal activity but we have no indication that the tumoricidal activity was mediated through a mIL-5-dependent mechanism.     

Rescue of the tumor-specific immune response of aged mice in vitro

In contrast to young mice, old mice fail to reject a transplanted challenge of the highly immunogenic, ultraviolet light-induced tumor 1591-RE. Old mice also fail to mount a cytolytic tumor-specific immune response in vivo, and spleen cells of old mice are defective in their ability to generate tumor-specific T cells in vitro. In the present study we report the results of cell culture mixing experiments that show that this deficiency is due to a decreased responsiveness of the Lyt-2+ tumor-specific cytolytic T cell precursors of the old animals. We also demonstrate with limiting dilution analysis that the defective responsiveness is not due to a clonal exhaustion of the precursors. In fact, the responsiveness could be restored in vitro by culturing the spleen cells of old animals at high density or by the addition of excess Lyt-1-/Lyt-2-/2000-rad-resistant spleen cells from young or old mice. Our results suggest that the rescue of tumor immunity in old individuals may be possible, perhaps by educating effector cells in vitro for adoptive immunotherapy.