Allogeneic tumor rejection induced by the intravenous injection of Lyt-2+ cytolytic T lymphocyte clones

Down-regulated expression of monocyte/macrophage major histocompatibility complex receptors in human and mouse monocytes by expression of their ligands

Mouse monocyte/macrophage major histocompatibility complex (MHC) receptor 1 (MMR1; or MMR2) specific for H-2D(d) (or H-2K(d) ) molecules is expressed on monocytes from non-H-2D(d) (or non-H-2K(d) ), but not those from H-2D(d) (or H-2K(d) ), inbred mice. The MMR1 and/or MMR2 is essential for the rejection of H-2D(d) - and/or H-2K(d) -transgenic mouse skin onto C57BL/6 (H-2D(b) K(b) ) mice. Recently, we found that human leucocyte antigen (HLA)-B44 was the sole ligand of human MMR1 using microbeads that had been conjugated with 80 types of HLA class I molecules covering 94·2% (or 99·4%) and 92·4% (or 96·2%) of HLA-A and B molecules of Native Americans (or Japanese), respectively. In the present study, we also explored the ligand specificity of human MMR2 using microbeads. Microbeads coated with HLA-A32, HLA-B13 or HLA-B62 antigens bound specifically to human embryonic kidney (HEK)293T or EL-4 cells expressing human MMR2 and to the solubilized MMR2-green fluorescent protein (GFP) fusion protein; and MMR2(+) monocytes from a volunteer bound HLA-B62 molecules with a Kd of 8·7 × 10(-9)  M, implying a three times down-regulation of MMR2 expression by the ligand expression. H-2K(d) (or H-2D(d) ) transgene into C57BL/6 mice down-regulated not only MMR2 (or MMR1) but also MMR1 (or MMR2) expression, leading to further down-regulation of MMR expression. In fact, monocytes from two (i.e. MMR1(+) /MMR2(+) and MMR1(-) /MMR2(-) ) volunteers bound seven to nine types of microbeads among 80, indicating ≤ 10 types of MMR expression on monocytes. The physiological role of constitutive MMRs on monocytes possibly towards allogeneic (e.g. fetal) cells in the blood appears to be distinct from that of inducible MMRs on macrophages toward allografts in tissue.

MHC class I recognition by monocyte-/macrophage-specific receptors

The most important transplantation antigens in the discrimination between "self" and "nonself" are encoded by genes in the major histocompatibility complex (MHC) locus (H-2 in mice). It has been assumed that T lymphocytes are the effector cells for allograft rejection, as athymic nude rodents fail to reject allografts. In 1988, we i.p. transplanted Meth A (H-2D(d)K(d)) tumor cells into C57BL/6 (H-2D(b)K(b)) mice and found macrophages to be cytotoxic against the allografts. In 1996, several groups using CD4 or CD8 knockout mice reported that non-T cells were the effector cells for the rejection of skin or organ allografts. In 1998, we ascertained that macrophages were the effector cells of skin allograft rejection. Recently, we isolated cDNA clones encoding monocyte/macrophage MHC receptors (MMRs) for H-2D(d) and H-2K(d); established H-2D(d)- and/or H-2K(d)-transgenic mice and lymphoma cells; and found, using MMR-deficient mice, that MMR and T-cell receptor were essential for the rejection of transgenic skin and lymphoma, respectively.

Spontaneous rejection of intradermally transplanted non-engineered tumor cells by neutrophils and macrophages from syngeneic strains of mice

It is not surprising that tumors arising spontaneously are rarely rejected by T cells, because in general they lack molecules to elicit a primary T-cell response. In fact, cytokine-engineered tumors can induce granulocyte infiltration leading to tumor rejection. In the present study, we i.d. injected seven kinds of non-engineered tumor cells into syngeneic strains of mice. Three of them (i.e. B16, KLN205, and 3LL cells) continued to grow, whereas four of them (i.e. Meth A, I-10, CL-S1, and FM3A cells) were spontaneously rejected after transient growth or without growth. In contrast to the i.d. injection of B16 cells into C57BL/6 mice, which induces infiltration of TAMs into the tumors, the i.d. injection of Meth A cells into BALB/c mice induced the invasion of cytotoxic inflammatory cells, but not of TAMs, into or around the tumors leading to an IFN-γ-dependent rejection. On day 5, the cytotoxic activity against the tumor cells reached a peak; and the effector cells were found to be neutrophils and macrophages. The i.d. Meth A or I-10 cell-immunized, but not non-immunized, mice rejected i.p.- or i.m.-transplanted Meth A or I-10 cells without growth, respectively. The main effector cells were CTLs; and there was no cross-sensitization between these two kinds of tumor cells, suggesting specific rejection of tumor cells by CTLs from i.d. immunized mice. These results indicate that infiltration of cytotoxic myeloid cells (i.e. neutrophils and macrophages, but not TAMs) into or around tumors is essential for their IFN-γ-dependent spontaneous rejection.

Rejection of intradermally injected syngeneic tumor cells from mice by specific elimination of tumor-associated macrophages with liposome-encapsulated dichloromethylene diphosphonate, followed by induction of CD11b(+)/CCR3(-)/Gr-1(-) cells cytotoxic against the tumor cells

Tumor cell expansion relies on nutrient supply, and oxygen limitation is central in controlling neovascularization and tumor spread. Monocytes infiltrate into tumors from the circulation along defined chemotactic gradients, differentiate into tumor-associated macrophages (TAMs), and then accumulate in the hypoxic areas. Elevated TAM density in some regions or overall TAM numbers are correlated with increased tumor angiogenesis and a reduced host survival in the case of various types of tumors. To evaluate the role of TAMs in tumor growth, we here specifically eliminated TAMs by in vivo application of dichloromethylene diphosphonate (DMDP)-containing liposomes to mice bearing various types of tumors (e.g., B16 melanoma, KLN205 squamous cell carcinoma, and 3LL Lewis lung cancer), all of which grew in the dermis of syngeneic mouse skin. When DMDP-liposomes were injected into four spots to surround the tumor on day 0 or 5 after tumor injection and every third day thereafter, both the induction of TAMs and the tumor growth were suppressed in a dose-dependent and injection number-dependent manner; and unexpectedly, the tumor cells were rejected by 12 injections of three times-diluted DMDP-liposomes. The absence of TAMs in turn induced the invasion of inflammatory cells into or around the tumors; and the major population of effector cells cytotoxic against the target tumor cells were CD11b(+) monocytic macrophages, but not CCR3(+) eosinophils or Gr-1(+) neutrophils. These results indicate that both the absence of TAMs and invasion of CD11b(+) monocytic macrophages resulted in the tumor rejection.

Acute Rejection of Allografted CTL-Susceptible Leukemia Cells from Perforin/Fas Ligand Double-Deficient Mice

The generation of knockout mice demonstrated that CD4(+), but not CD8(+), T cells were essential for the rejection of allografted skin or heart, presumably because these targets were CTL resistant. In the case of CTL-susceptible targets (e.g., P815 mastocytoma cells and EL-4 or RLmale1 T lymphoma cells), however, it is assumed that the CTL is the effector cell responsible for allograft rejection and that perforin and Fas ligand (FasL) pathways are the killing mechanisms. In the present study, we examined the role of these cytotoxic molecules in the rejection of i.p. allografted CTL-susceptible leukemia cells. Unexpectedly, the allografted leukemia cells were acutely rejected from gld (a mutation of FasL), perforin(-/-), or double-deficient mice. The peritoneal exudate cells from gld or normal mice showed T cell-, TCRalphabeta-, and perforin-dependent cytotoxic activity against the allograft, whereas the exudate cells from perforin(-/-) mice exhibited almost full cytotoxic activity in the presence of Fas-Fc. Furthermore, the infiltrates from double-deficient mice showed a high cytotoxic activity against the allografted cells even in the presence of anti-TCRalphabeta Ab or in the absence of T cells. The cytotoxic cells appeared to be macrophages, because they were Mac-1(+) mononuclear cells with a kidney- or horseshoe-shaped nucleus and because the cytotoxic activity was completely suppressed by the addition of N(G)-monomethyl-l-arginine, an inhibitor of inducible NO synthase. These results indicate that macrophages are ready and available to kill CTL-susceptible allografts when CTLs lack both perforin and FasL molecules.

Cellular basis of skin allograft rejection in mice: specific lysis of allogeneic skin components by non-T cells

BACKGROUND

It has been generally assumed that CD8+ T cells mediate direct lysis of allografts and that their growth, differentiation, and activation are dependent upon cytokine production by CD4+ T cells. However, both the generation of CD4- or CD8-deficient mice and adoptive transfer experiments with CD4+ T cells from CD8-deficient mice demonstrate that noncytotoxic CD4+ T cells alone are sufficient to induce skin or organ allograft rejection. Furthermore, we have reported that the major effector cells responsible for allografted-tumor (e.g., Meth A) rejection are allograft-induced macrophages (AIM) with MHC haplotype specificity.

METHODS

We characterized the macrophages migrating into the rejection site of allografted skin by immunohistochemical and in situ hybridization analyses using an antibody (K16.5) specific for AIM and a cDNA (pK30) encoding the antigen. To determine the in situ effector cells responsible for the rejection, we prepared both effector cells and target cells from the graft-graft bed border.

RESULTS

The macrophages seemed to be morphologically (monocytic), phenotypically (K16.5+/pK30+), and functionally (cytotoxic against Meth A cells) AIM. The AIM population in bulk infiltrates taken from the rejection site was cytotoxic against allografted, but not self, skin components (e.g., fibroblasts, myocytes, endothelial cells, and epithelial cells). In contrast, other types of infiltrating cells including lymphocytes and granulocytes were virtually inactive toward these targets, and NK-1.1+ cells hardly infiltrated into the rejection site.

CONCLUSIONS

These data suggest that the major effector cells mediating allografted skin rejection are AIM and not T cells.

Two distinct populations of primary cytotoxic cells infiltrating into allografted tumor rejection sites: infiltration of macrophages cytotoxic against allografted tumor precedes that of multiple sets of cytotoxic T lymphocytes with distinct specificity to alloantigens

It has been reported that the rejection of tumor allografts is mainly mediated by cytotoxic T lymphocytes (CTLs). Here, we characterized the cytotoxic effector cells of C57BL/6 (B6; H-2b) mice infiltrating into the rejection site of the i.p. allografted Meth A fibrosarcoma (or P815 mastocytoma) cells of H-2d origin. Two types of cytotoxic cells (i.e., CD8+ CTLs and macrophages (M phi s)) were identified by flow cytometric fractionation of the infiltrates or by specific in vitro elimination of cells either with antibody (Ab)-coated beads or with an Ab-plus complement. Of particular interest, these effector cells showed distinct and unique target specificities. First, the CTLs were inactive against transplanted tumor (e.g., Meth A) cells, whereas they were cytotoxic against donor-related concanavalin A (Con A) blasts as well as CTLL-2 (H-2b) cells transfected with a class I gene of H-2d origin. A cold target competition assay suggested that the CTLs were composed of multiple sets of T cells, each of which specifically recognized different allo-antigens. Second, the M phi s lysed the allografted tumor cells but were inert toward the Con A blasts and the CTLL-2 transfectants. Unexpectedly, the infiltration of M phi s preceded the infiltration of CTLs by several days during the course of rejection. These results indicate that two distinct populations of unique cytotoxic cells (i.e., CTLs and M phi s) are induced in the allografted tumor rejection site, and that the infiltration of cytotoxic M phi s responsible for rejection precedes that of the CTLs cytotoxic against cells expressing donor-related allo-antigens.

Failure to reject an allografted tumor after elimination of macrophages in mice

After an i.p. transplantation of an allogeneic tumor (Meth A) to C57BL/6 mice, a macrophage (M phi)-rich, non-T, non-NK cell population is induced as the major infiltrate and cytotoxic cells. We here evaluated the role of the M phi s in the rejection of allografted Meth A cells and characterized the M phi s in comparison with other well-known M phi s. At all time intervals after transplantation, the highest cytotoxic activities against Meth A tumor were obtained with the M phi-rich population. In addition, the lymphocyte-rich population had a significant but low cytotoxic activity, whereas two other population types, granulocytes and large granular cells, were inactive. When the M phi-rich or the T cell-depleted M phi-rich population was i.p. transplanted simultaneously with Meth A cells into untreated C57BL/6 mice, the tumor cells were rejected without growth. After specific elimination of M phi s by in vivo application of dichloromethylene diphosphonate-containing liposomes, the cytotoxic activity against Meth A cells was hardly induced at the transplantation site of Meth A cells and the allografted Meth A tumor continued to grow, indicating that a type of M phi is the effector cell essential for the rejection. In contrast to other well-known M phi s, the cytotoxic activity against Meth A cells was cell-to-cell contact dependent and soluble factor (e.g., NO and TNF-alpha) independent. Moreover, the cytotoxic activity of the M phi s (H-2b) against 51Cr-labeled Meth A (H-2d) cells was inhibited by the addition of unlabeled H-2d, but not H-2b, H-2k or H-2h, lymphoblasts as well as Meth A cells, implying the specific interaction of the M phi s with H-2d cells.

Establishment and characterization of transplantable tumor derived from a spontaneous malignant fibrous histiocytoma in the mouse

A tumor developed spontaneously in the subcutaneous tissue of the hind leg of a 7-month-old female ddY mouse. Light and electron microscopical examinations revealed that the original tumor was composed of an admixture of fibroblast-like and histiocyte-like cells arranged predominantly in a storiform or cartwheel pattern. The tumor cells gave positive reactions for acid phosphatase, N-acetyl-beta-glucosaminidase, non-specific esterase, beta-glucuronidase, alpha-1 antitrypsin and fibronectin. The original tumor was diagnosed as a malignant fibrous histiocytoma (MFH). The tumor was serially transplanted into syngeneic mice up to the 92nd generation. The tumor was also consistently transplanted into allogeneic mice of several inbred strains. The allogeneic mice used in the present study were strains having different H-2 haplotypes. During succeeding passages, transplanted tumors showed aberrant growth properties. The tumor transplanted into mice of inbred strains took well to back transplantation for mice of original strain and allotransplantation for other inbred strains. The pathological features of these transplantable tumors were basically similar to those of the original tumor. As mentioned above, a MFH developed spontaneously in the ddY mouse was consistently transplantable into both syngeneic and allogeneic mice.

Transplantability and MHC antigen expression of tumor mast cells

A cloned cell line was established from tumor cells spontaneously developed in a coculture of an autoreactive T cell line (1/+ T1) and 30 Gy-irradiated MRL/+ spleen cells with Con A supernatants. Morphological studies and studies of histamine content and modes of histamine release after stimulation with compound 48/80 revealed that the cell line (MRL-MC3) had mast cell characteristics. MRL-MC3 was transplantable not only to MRL/+, MRL/lpr and AKR/J (H-2k) mice but also to BALB/c and (BALB/c x DBA/2) F1 (H-2d) mice, although the allogeneic mice survived twice as long as syngeneic mice after i.v. injection. In addition, after i.v. injection, the mast cells infiltrated the livers and spleens of syngeneic (MRL/+) mice, however the lymph nodes around the mesenterium to the parapylorus in allogeneic (BALB/c) mice. A mast cell line (BALB-MC) was also established from a lymph node of MRL-MC3-injected BALB/c mice. Cell surface marker analyses revealed clear differences between the BALB-MC and the original MRL-MC3, which was positive for the expression of MHC class I antigens (K, D), I-E antigen and c-abl-encoded (anti-pEX-2 antibody-reactive) proteins, but not for I-A on the cell surface. In contrast, BALB-MC showed positive only for the MHC class I antigens (K, D) on the surface, and also positive for anti-pEX-2 antibody-reactive cytoplasmic proteins, as seen in MRL-MC3. Mast cells obtained from MRL-MC3-injected MRL/+ mice showed the same staining pattern as MRL-MC3. BALB-MC induced shorter survival times (approximately half) in both MRL/+ and BALB/c mice than MRL-MC3.(ABSTRACT TRUNCATED AT 250 WORDS)

Transplantation of CD4+ T cell clones into SCID mice

Engraftment of congenic (BALB/c) or semi-syngeneic (dm2) CD4+ T cell clones into immunodeficient SCID mice was investigated in two experimental systems: the adoptive transfer of Iad-restricted, anti-host-reactive ('self-reactive') CD4+ T cell clones, and the adoptive transfer of OVA-specific CD4+ T cell clones. SCID mice transplanted with 10(4)-10(5) purified BALB/c CD4+ T cells select anti-host-reactive T cells for engraftment. Anti-SCID-reactive T cell clones derived from such preselected CD4+ T cell populations could be successfully engrafted into secondary SCID recipients. In a second series of experiments, Iad-restricted, self-reactive BALB/c CD4+ T cell clones established in long-term culture from unselected, normal BALB/c spleen cell populations were transferred into SCID mice. Not a single clone from this panel could be transplanted into the immunodeficient host. Intravenous injection of OVA-primed dm2 (Ld-) CD4+ T cells into OVA-immunized young SCID (Ld+) mice repopulated the splenic and peritoneal T cell compartment of all transplanted mice. OVA-specific dm2 CD4+ T cells from the spleens of transplanted SCID mice were (sub)cloned under limiting dilution conditions in vitro. Only some of these clones repopulated OVA-immunized SCID recipients after retransplantation in vivo. Serial transfer experiments with a selected OVA-specific dm2 CD4+ T cell clone indicated that the route of cell transfer (i.p., but not i.v.), but not the route of OVA immunization of the host (i.v. or i.p.) were critical for successful engraftment of this clone. Hence, selected CD4+ T cell clones can be successfully engrafted into SCID mice if (i) the population from which clones are derived is preselected in SCID mice, (ii) the in vitro culture period of T cells is restricted to a few months, and (iii) alternative routes of cell transfer are tested. In infectious disease models, protective T cell clones can be identified in vivo using the described system. In addition, the importance of T cells with defined phenotype and effector functions in the pathogenesis of autoimmune disorders can be assessed in this system.

T cells expressing both L-selectin and CD44 molecules increase in number in peritoneal exudate cells and in vitro-stimulated spleen cells from mice immunized intraperitoneally with Listeria monocytogenes

L-selectin, which was first reported as MEL-14 antigen in mice, is a type of animal lectin and expressed on lymphocytes, neutrophils and macrophages. L-selectin has been reported to be a homing receptor of lymphocytes to peripheral lymph nodes and to have an important role in initial adhesion of lymphocytes and neutrophils to endothelial cells activated by inflammatory cytokines. On the other hand, it has been reported that naive T cells express L-selectin while memory T cells and in vitro antigen-stimulated T cells lose its expression. If all memory T cells lack L-selectin, trafficking of memory T cells into inflammatory sites would be difficult. To know whether all memory T cells lack L-selectin expression, kinetics of expression of L-selectin was analysed on memory T-cell subsets, which are detected by expression of CD44, in mice after intraperitoneal immunization with a sublethal dose of viable Listeria monocytogenes. T cells expressing both L-selectin and CD44 were detected in splenocytes and peritoneal exudate cells (PEC) from untreated mice, though at low levels. L-selectin+ CD44+ T cells increased in PEC, which are known to be highly enriched in antigen-primed T cells, and reached maximum level on day 14 after immunization. Furthermore, we found increases not only of L-selectin- CD44+ but also of L-selectin+ CD44+ T cells by in vitro Listeria antigen stimulation of Listeria-immune spleen cells on day 14. These results showed that T cells expressing both L-selectin and CD44 increase after antigen stimulation in vivo and in vitro. The L-selectin+ CD44+ T cells may be a subset of memory T cells which retain their capacity of trafficking to inflammatory sites.

Characterization of T lymphocyte clones isolated from BCNU-cured LSA mice

1,3-Bis(chloroethyl)-1-nitrosourea (BCNU) has been shown to "cure" over 90% of the mice bearing the syngeneic tumor LSA, and the cured mice acquire elevated levels of tumor-specific immunity. In the present study, we report for the first time the establishment and characterization of several tumor-specific CD8+ cytotoxic T cell (CTL) clones from splenic T cells of BCNU-cured LSA mice. Many of these clones were found to be strongly cytotoxic to LSA but not to a different H-2b tumor target such as EL-4, or the natural killer (NK)-susceptible target YAC-1, NK-resistant target P815, or con A or LPS blasts from H-2b mice. Some of the clones showed a moderate level of cytotoxicity to the NK-susceptible target YAC-1. The relative roles of interleukins such as IL-2, IL-4 or IL-6 in supporting the proliferative response of some LSA-activated CTL clones were analyzed. As expected, recombinant human (rh) IL-2 alone supported the proliferative response of activated CTL clones. Addition of recombinant murine (rm) IL-4 or rhIL-6 alone to the culture failed to influence the response. Also, in combination with rhIL-2, neither rmIL-4 nor rhIL-6 appreciably augmented rhIL-2-supported proliferative response of CTL clones. These studies may provide insights for the development of effective approaches to modulate function and activity of effector T cells.

Age-related decrement in cytotoxic T lymphocyte (CTL) activity is associated with decreased levels of mRNA encoded by two CTL-associated serine esterase genes and the perforin gene in mice

The age-related decline in cytotoxic T lymphocyte (CTL) activity has been recognized for many years. Age-related alterations in several immunologic events have been suggested to be partly or completely responsible for this decline. We had previously demonstrated (Bloom et al., Cell. Immunol. 1988. 144: 440) in mice that a deterioration in the lytic mechanism may be at least in part responsible for the decline in CTL activity. We now report that this decline correlates with an age-related decrease in serine esterase activity released into the supernatant medium in the process of generating CTL. Northern analyses were then used to examine the effect of age on expression of genes encoding for perforin and two CTL-associated serine esterases. The products of all three of these genes have all been postulated to play roles in CTL-mediated lysis. We show that the expression of all three of these genes appears to decline with age in the process of generating allogeneic CTL. These alterations in gene expression correlated both with diminished cytolytic and released esterase activities generated by mixed leukocyte culture in spleen cells of old mice compared to young. The age-related decline in gene expression could not be attributed to shifts in T cell subsets, but CD8+ cells generated by allogeneic stimulation of nylon wool-passed spleen cells from old mice expressed significantly less cytolytic activity than those from young. This report is the first demonstration of an age-related decrease in expression of a functionally related group of genes. In addition, these findings are compatible with the suggested roles for perforin and serine esterase release in CTL-mediated target cell lysis.

Cultured rat kidney parenchymal components are damaged by cytotoxic lymphocytes produced in MLC

Donor-specific cytotoxic lymphocytes (CTL) can be recovered from rejecting allografts both in animal models and in humans. These allograft infiltrating CTL expressing specific cytotoxicity to relevant MHC-restricted target cells in vitro most likely constitute the major effector arm during rejection. Effector cells with similar phenotype, specificity and function can be produced in mixed lymphocyte cultures (MLC). Despite the pivotal importance of CTL in allograft rejection, there is limited information about the susceptibility of different parenchymal graft cells to CTL-mediated damage. We used cultured rat glomerular epithelial cells (GEPC), glomerular mesangial cells (GMC), tubular cells (TC) and heart endothelial cells (HEC) as distinct parenchymal target components in 4 h Chromium release assays. All of these graft components were damaged by CTL produced in 6-day MLC (specific release: 10-25%). Three-day gamma-interferon (IFN-G) treatment enhanced MHC class I and II surface expression on all our targets and increased their susceptibility for CTL-mediated lysis in our experiments (specific release: 20-60%).

High proliferative capacity and specific antiautologous melanoma cytotoxicity of a human T-lymphocyte clone derived from tumor-infiltrating lymphocytes

A CD8+ clone, identified by its T-cell receptor gamma- and beta-gene configuration, was shown to preferentially develop, in the bulk culture of melanoma tumor-infiltrating lymphocytes with recombinant interleukin 2 after 1 month. Thirteen CD8+ clones were obtained by limiting dilution culture of tumor-infiltrating lymphocytes from 43-days old culture. Four of these clones, analyzed for T-cell receptor rearrangements, exhibited exactly the same T-cell receptor gene pattern as tumor-infiltrating lymphocytes from the bulk culture, showing, therefore, that all the CD8+ clones were subclones. All the 13 CD8+ subclones were strongly cytotoxic for autologous melanoma cells but did not kill K562. A more complete cytotoxicity analysis showed that the clones did not kill autologous fibroblasts or Con A blasts or allogeneic tumor targets. Furthermore, specific killing was inhibited by monoclonal antibodies against CD3, CD8, T-cell receptors alpha beta, and class I major histocompatibility complex antigens indicating that effector-to-target cell recognition was mediated through the T-cell receptor in a major histocompatibility complex-restricted fashion. These data showed that human melanoma-specific cytotoxic T lymphocytes can be obtained from melanoma TIL and that a single cytotoxic T lymphocyte clone can be expanded to more than 10(10) cells without a loss of autotumor specificity.

Treatment with interleukin-2 in an immunodepressed state

Cytotoxic T-lymphocyte (CTL) and lymphokine activated killer (LAK) cell (fraction II) precursors with a density of 1.077-1.067 g/ml and suppressor cells (fraction I) with a density of 1.067-1.056 g/ml were isolated by the separation of cancer patient peripheral blood mononuclear cells (MNC) on a Percoll gradient. Cells from fraction I inhibited the generation of CTL in mixed lymphocyte-tumor culture (MLTC) and LAK cells when added to fraction II lymphocytes at a ratio of 1:1 at the beginning of the culture. The effect was dependent on the dose of added suppressor cells and resistant to mitomycin-C treatment. Treatment of cell fractions prior to culture with monoclonal antibodies and complement showed that CTL precursors and suppressor cells were OKT3+/OKT8+. Cells from fraction I possessed suppressor activity in all patients examined but only in 4 of 10 healthy donors. Studies of monocytes and T-lymphocytes isolated from fraction I demonstrated that in cancer patients both monocytes and T-lymphocytes functioned as suppressors whereas in healthy donors, the monocytes mediated suppression. The data obtained provide evidence for an increased suppressor cell activity in cancer patients which can inhibit the generation of cytotoxic antitumor response with interleukin-2 (IL-2) in vitro.

Lymphocyte homing

The phenomenon of "homing" is discussed with respect to patterns of lymphocyte circulation and the molecules on the surface of both endothelium and lymphocytes that mediate this process. In addition, the data are analysed in the context of a model for lymphocyte homing.

Lymphokine-activated tumor inhibition: combinatory activity of a synthetic nonapeptide from interleukin-1, interleukin-2, interleukin-4, and interferon-gamma injected around tumor-draining lymph nodes

This report initially reviews the progressive steps of research designed to build up a new, well-defined helper system triggering both the non-specific and the tumor-specific immune reactivity of a host bearing a tumor, in order to impair tumor growth. Tumor-specific T-helper lymphocytes were first generated in vitro from the spleen of mice with evident tumors. As these lymphocytes inhibit tumor growth by recruiting host reactivity through the release of lymphokines, the peri-tumoral injection of interleukin-2 (IL-2) was then experimented. Repeated injections of 10 units of IL-2 are only weakly effective, but its triggering of an efficient anti-tumor reactivity is markedly enhanced when non-reactive lymphocytes directly obtained from tumor-bearing mice are artificially admixed with the challenge tumor cells. Lastly, in order to ascertain whether lymphocytes themselves could be dispensed with, lymphokines were injected around tumor-draining lymph nodes. Ten daily injections of 1 pg of the 163-171 synthetic nonapeptide of human IL-1 beta appeared very efficient in activating tumor inhibition, particularly when combined with IL-4 or (to a lesser extent) IL-2.

Helper strategy in tumor immunology: expansion of helper lymphocytes and utilization of helper lymphokines for experimental and clinical immunotherapy

Two main kinds of immune strategy are possible against neoplasia. The first potentiates a selected effector arm. In vitro culture with exogenous interleukin-2 (IL-2) increases the activity of natural killer cells and leads to the expansion of T cytotoxic lymphocytes. Systemic reinfusion of both of these cells with high doses of IL-2 mediates the regression of a variety of murine and human tumors. In an alternative strategy, a few regulatory lymphocytes turn on immune reactivity by triggering a cascade of interconnected effector functions. The efficacy of this strategy rests on the repertoire of effector mechanisms moved to action. An effective immunoregulatory maneuver is the addition of helper determinants on the surface of tumor cells. Its power can be further increased by the pre-induction of helper T lymphocytes specific to the helper determinants. This approach can be achieved in mice by coupling muramyl dipeptides to tumor cells, along with eliciting T lymphocytes specifically reactive to Bacillus Calmette-Guerin. Noncytotoxic T helper lymphocytes produce factors which recruit nonspecific (macrophages) as well as specific (cytolytic T lymphocytes) anti-tumor attacking cells. In this way protection can be afforded against primary tumors and metastases, as well as leukemia cells. As the activity of helper lymphocytes rests mostly on lymphokine release, the use of molecularly defined lymphokines mimicking T-helper functions has also been attempted. In a few experimental models, the association of low doses of IL-2 with non-reactive lymphocytes from tumor-bearing mice promotes an effective anti-tumor reaction in the host. Moreover, the combination of distinct lymphokines can also build a molecularly defined helper system able to activate in sequence non-specific and specific anti-tumor reactions in vivo. Trials intended to evaluate the clinical impact of these helper approaches in the management of human tumors are being started or are already under way.

Low doses of interleukin 2 induce bystander cell lysis by antigen-specific CD4+ inflammatory T cell clones in short-term assay

The effect of recombinant interleukin 2 (rIL2) and interferon-gamma (IFN-gamma) on the cytolytic activity of a CD4+ class II major histocompatibility complex-ovalbumin (OVA)-specific murine clone called 5.8.6 was examined. Low doses of IL2 (0.1-1.0 U/ml) induce clone 5.8.6 to kill in an antigen-independent fashion in short-term 51Cr-release and 3H-release assays (6-12 h). Targets killed by 5.8.6 cells include P815, YAC-1 and B lymphoma cells. IFN-gamma, alone or in combination with IL2, has no effect. 5.8.6 and similar inflammatory CD4+ T cell clones have been shown to lyse bystander target cells in the presence of a specific stimulator target. We propose that killing of bystander targets by clone 5.6.8 is due to nonspecific cytolytic activity induced by the clone's own IL2 secreted in response to recognition of the specific target.

Induction of tumor suppression and delayed-type footpad reaction by transfer of lymphocytes sensitized to a xenogenized tumor variant

Splenocytes immune to a highly immunogenic ("xenogenized", L5178Y/DTIC) variant of a murine lymphoma exert anti-parental-tumor activity in a systemic adoptive transfer system, the effect being apparently associated with the Lyt-2- fraction of the lymphocyte population. During investigation of the mechanisms of this protection, we found that the L5178Y/DTIC tumor-immune lymphocytes exhibited an appreciable anti-L5178Y delayed-type hypersensitivity (DTH) response. Enrichment of those lymphocytes in L3T4+ cells significantly enhanced the protective effect as well as the DTH reaction, whereas the use of an anti-L3T4 but not anti-Lyt-2 reagent blocked both activities. In vitro, lymphocyte proliferation against L5178Y cells occurred and was apparently associated with the Lyt-2- fraction of a population of L5178Y/DTIC immune splenocytes.

Evidence for involvement of dual-function T cells in rejection of MHC class I disparate skin grafts. Assessment of MHC class I alloantigens as in vivo helper determinants

The present study further characterizes the cellular mechanisms involved in the in vivo rejection of MHC class I-disparate skin allografts. Previously, we demonstrated that class I-specific rejection responses could result from collaborations between distinct populations of lymphokine-secreting T helper (Th) and lymphokine-responsive T effector (Teff) cells. In the present study, we have assessed the possibility that class I-specific rejection responses could also result from a second cellular mechanism involving a single population of dual-function Th/Teff cells that would not have any further requirement for cell-cell collaboration. Our experimental strategy was to determine the ability of MHC class I-allospecific T cells, in response to class I allodeterminants expressed on skin grafts, to provide help in vivo for activation of helper-dependent Teff cells. We found that class I anti-Kbm1-allospecific T cells would reject bm1 skin allografts, but would not generate help for the activation of helper-dependent effector cells that were specific for third-party skin allografts (e.g., grafts expressing Kbm6, Qa1a, or H-Y allodeterminants). This failure of anti-Kbm1 T cells to provide help in response to bm1 skin allografts was not due to an inability of lymphokine-secreting anti-Kbm1 Th cells to recognize and respond in vivo to Kbm1 allodeterminants expressed on skin, since lymphokine-secreting anti-Kbm1 Th cells were specifically primed in animals engrafted with bm1 skin allografts. Nor was any evidence found that this failure was due to active suppression of anti-Kbm1 helper activity. Rather, we found that anti-Kbm1 T cells consumed nearly all of the helper factors they secreted. Taken together, these results are most consistent with the in vivo activity of dual-function Th/Teff cells that consume the lymphokines they secrete. Thus, this study demonstrates that MHC class I-disparate skin allografts can be rejected by two mechanisms, depending on the ability of the allospecific Teff cell to secrete helper lymphokines. MHC class I-disparate grafts can be rejected by (a) class I-allospecific Teff cells that are unable to produce lymphokine but are responsive to exogenous T cell help; and (b) class I-allospecific dual-function Th/Teff cells that are able to both produce and consume soluble lymphokine.

Autologous lymph node cell-derived tumor-specific cytotoxic T-cells for use in adoptive immunotherapy of human melanoma

The in vitro development of tumor-specific cytotoxic T-cells from draining and tumor-involved lymph nodes obtained from melanoma patients were examined. Fresh draining or tumor-involved lymph node cells (LNC) demonstrate no significant cytotoxic activity against a variety of tumor targets including autologous melanoma. Natural killer cell (NK) activity is very low or absent in all of these specimens. Culture of the cells with irradiated autologous tumor and expansion in recombinant interleukin 2 (rIL-2) results in strong cytotoxicity for autologous tumor cells. The cultured cells are T-cells of mixed CD4 and CD8 phenotypes. Following restimulation with autologous tumor, these lines are capable of becoming specifically cytotoxic for autologous tumor as tested in direct killing and in cold target inhibition studies. The LNC yield from fresh specimens ranges from 1 X 10(7) to more than 1 X 10(9) cells averaging 5 X 10(8) cells. After the cells are cultured, we can achieve up to a 60-fold or more increase in cell numbers, that demonstrate strong cytotoxicity for melanomas. The potential for adoptive immunotherapy using such specifically sensitized cytotoxic T-cells of mixed phenotypes is discussed.

Age-related decline in the lethal hit but not the binding stage of cytotoxic T-cell activity in mice

The activity of allogeneic cytotoxic T lymphocytes (CTL) declines with aging, as measured at the population level in chromium release assays, and is associated with a decreased proliferative response to the inducing alloantigens. At the single cell level, no difference was noted between target binding cells obtained from alloantigen-stimulated spleen cells of young and old mice. However, a consistent, large, and significant difference was observed between CTL generated from the spleens of young and old mice in the percentage of bound effector cells with lysed targets, i.e., the percentage of killer cells. These results show age-related changes in the lethal hit stage and not the binding stage of CTL activity. This change could be used as a probe to identify the important mechanism(s) which mediates CTL activity.

Active specific immunotherapy with extracted tumor-specific transplantation antigen, cyclophosphamide, and adoptive transfer of tumor-specific cytotoxic T-cell clones

An L3T4-, Lyt2+ tumor-specific, cloned T-lymphocyte cell line (RTT-2) was isolated from a spleen cell population harvested from C3H/HeJ mice, following in vivo immunization against a syngeneic MCA-induced fibrosarcoma (MCA-F) and in vitro restimulation with 1-butanol-extracted, isoelectrophoretically purified MCA-F tumor-specific transplantation antigen (TSTA). RTT-2 required exposure to homotypic-extracted MCA-F TSTA in combination with low-dose IL-2 to maintain its specific cytotoxic activity in vitro. In vivo local adoptive transfer of RTT-2 caused specific neutralization of homotypic MCA-F, but not heterotypic MCA-D, tumor cells. Systemic in vivo transfer of RTT-2 alone augmented host resistance. In combination with a triple regimen of weekly doses of purified TSTA (1 microgram SC) and a single ip injection of CY (20 mg/kg), adoptive transfer of RTT-2 cells (1 X 10(7)) retarded the neoplastic outgrowth in and prolonged the survival of primary hosts bearing 3-, 7-, and 14-day established MCA-F tumors. In a spontaneous pulmonary metastasis model following amputation of a tumor-bearing limb, the triple regimen of TSTA/CY/RTT-2 markedly reduced the number of lung colonies. Thus RTT-2, which displays specific tumoricidal activity in vitro and in vivo, may afford a suitable tool to dissect T-cell receptors recognizing tumor markers on 1-butanol-extracted, MCA-F TSTA.

Inhibition of murine lymphoma growth by adoptive transfer of lymphocytes sensitized to a xenogenized tumor variant

Lymphocytes immune to a highly immunogenic ("xenogenized") variant of a murine lymphoma--which were shown to exert anti-xenogenized tumor activity in a previously described model of tumor immunotherapy--were tested in the present study for possible suppressive effects on the growth of an i.c. graft of the original lymphoma. Remarkable tumor-inhibitory effects followed the i.v. infusion of splenic lymphocytes sensitized or restimulated in vitro, or derived from animals immunized in vivo with the xenogenized tumor cells. The pattern of inhibition of the parental cells was apparently similar to that previously described for the xenogenized variant, but preliminary evidence suggests that the underlying mechanisms may be different.

Specific cytotoxic T cells are found in the nonrejected kidneys of blood-transfused rats

Preoperative, donor-specific blood transfusion leads to indefinite survival of rat renal allografts in the strain combinations used. 51Cr-release assays have shown that the level of specific cytotoxic effector activity in the grafts of transfused (nonrejected kidney) animals is very high and may equal or exceed that seen in the grafts of untreated (rejected kidney) recipients. Such cytotoxicity demonstrates specificity for the alloantigens of the kidney, is T cell-mediated, and may persist within the transplant.

Discrimination of human cytotoxic lymphocytes from regulatory and B-lymphocytes by orthogonal light scattering

Light scattering properties of human lymphocyte subpopulations selected by immunofluorescence were studied with a flow cytometer. Regulatory and B-lymphocytes showed a low orthogonal light scatter signal, whereas cytotoxic lymphocytes identified with leu-7, leu-11 and leu-15 revealed a large orthogonal light scatter signal. Two populations in light scatter histograms could be observed with monoclonal antibodies directed against determinants present on both regulatory and cytotoxic lymphocytes. By analysis of the lymphocytes of 16 individuals we found a linear relation between the number of cells with a large orthogonal light scattering and the number of cytotoxic lymphocytes identified with leu-7, leu-11 and leu-15. These observations demonstrate physical differences between cytotoxic lymphocytes and regulatory and B lymphocytes. Moreover, the results suggest a method to estimate the amount of cytotoxic lymphocytes without using monoclonal antibodies.

Tumour inhibition by interleukin-2 at the tumour/host interface

Until recently, lymphokines were regarded suspiciously as 'ill-defined factors'. Today, however, some of them have been clearly defined in both structural and functional terms. The interleukin-2 (IL-2) molecule and its specific membrane receptors have been the subject of particular attention. Endogenous IL-2 has proved to be an important signal for the activation and expansion of various cell-mediated immunity functions, while exogenous IL-2 has been used to activate numerous cell functions, both in vitro and in vivo, as well as in tumour immunotherapy, both alone or combined with lymphocytes previously activated in vitro (lymphokine-activated killer cells). Adoptive transfer of these cells together with high doses of IL-2 is particularly promising from the clinical standpoint, though by no means free from problems. IL-2 can also be employed in small doses locally in the presence of non-activated lymphocytes from tumour bearing mice to induce a local reaction that subsequently becomes systemic and can lead to the rejection of incipient tumours. Various host immune cells, primarily eosinophils and lymphocytes are involved in this reaction, which can also give rise to tumour-specific immune memory. In this way, the host immune system, despite its inevitable defeat in the first battle against a tumour, may acquire an important role in the long war that lies ahead.

T-cell responses at the host: tumour interface

The evidence considered here reinforces the conclusion that T-cell responses to tumours involve complex cellular interactions. An attempt to summarize some of these interactions is shown. This emphasizes that not only are the interactions between the effector cell populations complicated, but that the target cell surface is also subject to variation and modification as a result of the immune response. A feature that also emerges from these studies is that most cells apparently responding to or infiltrating a tumour do not necessarily participate in its destruction, and it is in this area that experimental tumour systems have particular value. This also perhaps explains the preoccupation of experimentalists with the identification of 'the' effector cell crucial to tumour rejection. However, there is heterogeneity between systems in terms of the type of rejection response induced, but a logical basis for this heterogeneity is not established. If experimental studies could define the nature of the immune response generated by a tumour in the context of the biological features of the tumour itself, this could lead to the prediction of the immunogenicity and potential for induction of a rejection response for that tumor. Clearly, experimental tumour systems do not provide an exact reflection of the situation with human tumours. However, they may provide systems that illuminate particular aspects of the human response, and give precedents to guide the interpretation of data derived from human systems. This form of assessment is still at an early stage, but developments in the experimental field should provide a framework for the development and exploitation of T-cell responses to tumours.

Analysis of T-cell subsets in rejection of Kb mutant skin allografts differing at class I MHC

The T-cell subpopulations which initiate and mediate tissue allograft rejection remain controversial. In the present study we attempted to identify the phenotype and function of the T-cell subset(s) primarily responsible for the rejection of skin allografts differing at a single class I locus in the major histocompatibility complex (MHC). We found that the rejection rates by B6 mice (H-2b) of four different class I mutant (Kbm) skin allografts form a distinct hierarchy. This hierarchy correlates strikingly and uniquely with the relative precursor frequencies of Lyt2+ interleukin-2-secreting T-helper cells reactive against the various Kbm mutants. To investigate the role of Lyt2+ T cells in the rejection of class I-disparate skin allografts directly, H-2b nude mice were engrafted with Kbm skin allografts and then reconstituted with L3T4+ or Lyt2+ T-cell subpopulations from syngeneic H-2b mice. Lyt2+ T cells were observed to be both necessary and sufficient for the rejection of class I-disparate Kbm skin allografts, whereas L3T4+ T cells were neither necessary nor sufficient. These results identify the Lyt2+ interleukin-2-secreting T-cell subset as the critical cell type determining the rejection rate of class I-disparate Kbm skin allografts.

Enhancement of the generation of cytotoxic T cells by endogenous opiates

Previous reports have shown that endogenous opiates (beta-endorphin and met-enkephalin) have effects on cells of the immune system at physiologic concentrations. Using murine spleen cells, we herein report that beta-endorphin and met-enkephalin can enhance the generation of cytotoxic T lymphocytes (CTLs) at suboptimal concentrations of alloantigen in a one-way mixed lymphocyte culture (MLC). This enhancement is seen at levels ranging from 2.9 X 10(-8) M to 2.9 X 10(-14) M and 1.45 X 10(-6) M to 1.45 X 10(-12) M for beta-endorphin and met-enkephalin, respectively. This enhancement can be partially blocked by naloxone at 10(-7) M. Furthermore, the simultaneous addition of met-enkephalin and beta-endorphin does not increase the enhancement of CTL generation by either opiate peptide alone suggesting that they are acting through the same receptor. This report gives added proof for the regulatory-loop theory between the neuroendocrine and immune systems.

Graft rejection following HLA matched T-lymphocyte depleted bone marrow transplantation

Bone marrow graft rejection following HLA-matched bone marrow transplantation (BMT) for leukaemia has been a rare problem. However, with the introduction of T-lymphocyte depleted BMT, graft rejection is recognized as a new complication. At the Royal Free Hospital (RFH) in London T-depletion is achieved using two monoclonal antibodies with complement mediated lysis. The methodology was extended to other centres and in total 56 patients have received T-depleted, HLA matched BMT. Twelve of 56 patients have had graft rejection. At the RFH three of 41 (7%) patients have had rejection whereas at collaborating centres nine of 15 (60%) patients have had rejection. We have investigated these rejections in order to identify factor(s) responsible. Rejection was not restricted by patient or donor characteristics, nor disease status. Patient management, chemotherapy conditioning, efficiency of T-depletion, graft versus host disease (GvHD), and infection post BMT, were not consistently implicated. The major difference between the RFH and all other centres was in the radiotherapy (RT) conditioning: The RFH prescribed a single fraction of 7.5 Gy total body irradiation (TBI) whilst collaborating centres gave 10 or 12 Gy fractionated TBI. We conclude that the different incidence of rejection (7% v. 60%) relates primarily to the RT conditioning although the mechanisms(s) of rejection remain unknown. We conclude that where T-depleted BMT is used, compensation by more intensive RT conditioning is required in order to avert graft rejection.

Antigen-driven long term-cultured T cells proliferate in vivo, distribute widely, mediate specific tumor therapy, and persist long-term as functional memory T cells

Mice bearing disseminated syngeneic FBL-3 leukemia were treated with cyclophosphamide plus long term-cultured T cells immune to FBL-3. The cultured T cells for therapy had been induced to grow in vitro for 62 d by intermittent stimulation with irradiated FBL-3. At the time of therapy, such antigen-driven long term-cultured T cells were greatly expanded in number, proliferated in vitro in response to FBL-3, and were specifically cytotoxic. Following adoptive transfer, donor T cells persisting in the host were identified and counted using donor and host mice congenic for the T cell marker Thy-1. The results show that antigen-driven long term-cultured T cells proliferated rapidly in vivo, distributed widely in host lymphoid organs, and were effective in tumor therapy. Moreover, the already rapid in vivo growth rate of donor T cells could be augmented by administration of exogenous IL-2. When cured mice were examined 120 d after therapy, donor L3T4+ T cells and donor Lyt-2+ T cells could be found in large numbers in host ascites, spleen, and mesenteric and axillary lymph nodes. The persisting donor T cells proliferated in vitro, and became specifically cytotoxic in response to FBL-3, demonstrating that antigen-driven long term-cultured T cells can persist long term in vivo and provide immunologic memory.

Early transmembrane events in alloimmune cytotoxic T-lymphocyte activation as revealed by stopped-flow fluorometry

We have studied early transmembrane events in mouse alloimmune cytotoxic T-lymphocyte (LC7, H-2b) activation by specific target cells (mouse mastocytoma P815, H-2d) and a mitogenic lectin, Con A, by using stopped-flow fluorometry with three different fluorescent probes. After binding to target cells (P815), cytotoxic T lymphocytes (LC7) first increased their membrane fluidity and, then, calcium was released from intracellular stores. After that, there was a calcium influx from the external medium into the T lymphocytes. This calcium influx was blocked by calcium antagonists (verapamil or diltiazem). The same sequence of events was also observed in the activation of T lymphocytes (LC7) by Con A and in the response of specific target cells (P815) after cytotoxic T lymphocytes (LC7) binding. Nonspecific (syngeneic) target cells (mouse lymphoma EL-4, H-2b) did not cause any early transmembrane events in cytotoxic T lymphocytes (LC7, H-2b).

Adoptive immunotherapy of cancer with immune and activated lymphocytes: experimental and clinical studies

Recent studies of passive adoptive immunotherapy of experimental tumors indicate that histologically different neoplasms can be cured by this procedure in mice, rats and guinea pigs. In this paper two main approaches of adoptive immunotherapy with lymphocytes are considered. One which makes use of specific tumor-immune cells and is applicable to immunogenic tumors, and the other which uses activated (allostimulated and/or IL-2-activated) lymphocytes and is applicable to immunogenic and non-immunogenic neoplasms. Experimental models of both approaches and results provided by them are reviewed. These studies indicate that transfer of tumor-reactive lymphocytes with or without the combined administration of IL-2 into syngeneic tumor-bearing animals can lead to the eradication of a disseminated neoplasia when certain conditions are met. In particular, it was found that high tumor burdens, delay of treatment and low number of transferred lymphocytes can adversely affect the results. It has also been shown that the therapeutic effect of treatment with anti-cancer drugs or irradiation may be significantly improved by the addition of adoptive immunotherapy. The successful treatment of immunogenic tumors often requires the inhibition of suppressor lymphocytes by Cy or irradiation. Non-immunogenic tumors can be successfully treated only by providing activated lymphocytes and high doses of IL-2. Recent findings of few available human studies of adoptive immunotherapy are also reviewed, and the problems of toxicity and possible therapeutic effects of infusion of autologous, activated lymphocytes and IL-2 are discussed.

Augmentation of the therapeutic efficacy of adoptive tumor immunotherapy by in vivo administration of slowly released recombinant interleukin 2

Immunization of C57BL/6 mice with MMC-treated syngeneic lymphoma cells, MBL-2, caused the generation of antitumor effector cells in vivo and the immunized mice permanently rejected viable MBL-2 lymphoma cells. Both plastic nonadherent T cells and plastic adherent M phi obtained from MBL-2 immunized mouse peritoneal exudate cells revealed strong cytotoxic activity against MBL-2 lymphoma cells, whereas immune spleen cells were not highly active against MBL-2 lymphoma cells in vitro. However, systemic adoptive transfer of immune spleen cells into the MBL-2-bearing mice by i.v. infusion in conjunction with i.p. cyclophosphamide (100 mg/kg) treatment cured the mice of tumor. This therapeutic efficacy of immune spleen cells was reflected by the number of transferred effector cells and over 5 X 10(7) immune spleen cells were required to cure the mice completely. The cells mediating in vivo rejection of MBL-2 lymphoma cells were Thy 1.2+ T cells. This ACIT was specific against MBL-2 lymphoma cells and had no effect on the growth of other syngeneic tumors, B16 melanoma or BMC6A fibrosarcoma. In vivo administration of recombinant interleukin 2 (r-IL2) combined with ACIT greatly modulated the cure rate of tumor-bearing mice. In addition, we found that slowly released r-IL 2 administratered from an ALZET miniosmotic pump was more effective in augmenting the therapeutic efficacy of immune spleen cells in ACIT than a single injection of the same total dose of r-IL 2.

Human T cell clones express functional homing receptors required for normal lymphocyte trafficking

To function efficiently in vivo, lymphocytes must circulate from the blood into lymphoid tissues and other sites of immune reaction. Herein, we show that human cytotoxic and helper T cell clones and lines, maintained in vitro with IL-2, express the functional capacity to recognize and bind to high endothelial venules (HEV), a capacity essential for lymphocyte exit from the blood, and hence for normal lymphocyte trafficking. The expression of functional homing receptors distinguishes human T cell clones from their murine counterparts, which uniformly lack receptors for HEV and are unable to migrate normally from the blood in vivo. The results raise the possibility that human T cell clones may be more effective in mediating in vivo immune responses than is suggested by murine models.

Effector mechanisms of syngeneic anti-tumour responses in mice. II. Cytotoxic T lymphocytes mediate neutralization and rejection of radiation-induced leukaemia RL male 1 in the nude mouse system

We demonstrated the efficacy of a long-term cultured cytotoxic T-lymphocyte line, CTLL-D4, on tumour growth inhibition using athymic nude mice as recipients. CTLL-D4, specific for a unique surface determinant on a radiation-induced leukaemia RL male 1 of BALB/c origin, was obtained from the limiting dilution culture of MLTC cells performed between spleen cells of a CB6F1-nu/+ mouse immunized in vivo and RL male 1 stimulator cells, and cultured for several months in the absence of added TCGF as described in our preceding paper (Kuribayashi, 1985). The specific inhibition of tumour growth by CTLL-D4 was demonstrated both in Winn-type neutralization assay and in systemic transfer experiments. A subcutaneous inoculation of the mixture of CTLL-D4 and RL male 1 cells resulted in the complete inhibition of tumour growth, even at the effector to tumour cell ratio of 1:1, whereas non-cytolytic D4f, which was self-Ia antigen(s)-reactive, composed entirely of Lyt-1+23- T cells and derived originally from CTLL-D4 but completely lost its cytotoxic activity during culture with the irradiated syngeneic feeder cells alone, had no inhibitory effect at all. In the adoptive transfer studies, the subcutaneously established tumours were rejected by the single i.v. transfer of 2 X 10(7) CTLL-D4 cells into CB6F1-nu/nu mice. However, D4f was ineffective again in this systemic transfer system. When the effect of CTLL-D4 cells on tumour rejection in vivo was compared to that of non-cultured spleen cells hyperimmunized with RL male 1 cells, the former exhibited more rapid rejection in nude mice after i.v. transfer than the latter did, suggesting that CTLL-D4 cells also attack the tumour cells much more effectively as effectors in vivo. Thus, it is conceivable that CTLs are mainly involved in tumour rejection in this adoptive transfer system using RL male 1 tumour cells and athymic nude mice.

Interstitial murine cytomegalovirus pneumonia after irradiation: characterization of cells that limit viral replication during established infection of the lungs

Interstitial pneumonia associated with viral replication in lung tissue was observed after cytomegalovirus infection of total-body gamma-irradiated mice, whereas in noncompromised hosts the lungs were not affected and virus multiplication was restricted to the salivary glands. The radiation damage could either predispose normally nonpermissive cell types for productive infection or abrogate an immune control of the tissue manifestation of infection by elimination of lymphocytes. Adoptive transfer of lymphoid cells into irradiated, infected recipients supported the second alternative. Even when infection was established in the lungs, as manifested by the presence of infected lung tissue cells in the alveolar septa, an antiviral effect could be assigned to the Lyt-2+, L3T4- subset of T lymphocytes specifically sensitized in the immunocompetent donor. These cells did not require in vitro propagation to perform effector cell functions in vivo and were operative under physiological conditions in comparatively low numbers. Hence, there is reason to assume that T lymphocytes are responsible for the tissue distribution of cytomegalovirus replication during infection.

Adoptive immunotherapy of intracerebral murine lymphomas: role of different lymphoid populations

In an attempt to elucidate the cellular mechanisms responsible for the therapeutic activity of systemic immunotherapy in an adoptive transfer system, lymphoma cells were implanted i.c. It was found that, upon peripheral injection of cytotoxic T-lymphocytes with specificity for the tumor, the cells reached and infiltrated the diseased brain but did not accumulate selectively in the malignant graft. In order to accomplish significant tumor inhibition, the infused lymphocytes, largely expressing the Lyt-1+2+ phenotype, apparently cooperated with radioresistant phagocytic cells present in histocompatible hosts and athymic mice.

A novel serine esterase expressed by cytotoxic T lymphocytes

Cytotoxic T (Tc) lymphocytes recognize and lyse target cells and are thought to serve as an important defence against viral infections and possibly against neoplasms. The nature of the receptors responsible for antigen recognition by these cells is becoming clearer, but the molecular mechanisms responsible for their cytolytic activity remain largely unknown. The possibility that proteases are involved in this process has been suggested by the effects of certain inhibitors. Here we demonstrate that clones of murine Tc cells possess considerable trypsin-like esterase activity when assayed by a sensitive colorimetric assay. This activity was blocked completely by two serine esterase inhibitors, diisopropylfluorophosphoridate (DFP) and phenylmethylsulphonyl fluoride (PMSF), but not by N alpha-tosyl lysyl chloromethyl ketone (TLCK). The use of 3H-DFP as an affinity-labelling reagent demonstrated that the esterase activity resides in a protein of relative molecular mass (Mr) 28,000 (28K). A wide variety of other lymphocytes, including those from thymus, spleen and lymph node, established lines of B cells and noncytotoxic T cells, and clones of T helper cells, had about 300-fold less esterase activity than the Tc-cell clones and far smaller amounts of the DFP-reactive 28K protein. However, in thymocytes the esterase activity increased 20-50-fold and the 28K protein became more prominent 4 days after these cells had been stimulated in vitro to generate Tc cells.