Heated lymphocytes express HLA-DR antigens despite their inability to stimulate in MLC

Effect of hyperthermia in vitro and in vivo on adenine and pyridine nucleotide pools in human peripheral lymphocytes

Hyperthermia has been shown in vitro and in vivo to potentiate the effects of ionizing irradiation. Previous studies found that hyperthermia alters the metabolism of adenosine diphosphate (ADP)-ribose polymers required for recovery from DNA damage and that poly(ADP-ribose) polymerase activity is very sensitive to cellular nicotinamide-adenine dinucleotide (NAD) levels. Thus, the effect of 41.8 degrees C hyperthermia in vitro and in vivo on NAD and adenosine triphosphate (ATP) levels was studied in human peripheral lymphocytes. In vitro studies showed significant decreases in oxidized NAD (NAD+) and ATP levels after heating that simulated a clinical whole-body hyperthermia (WBH) treatment. This nucleotide depletion could not be attributed to nucleotide leakage or increased enzymatic NAD+ consumption. As the reduction of NAD observed was sufficient to decrease poly(ADP-ribose)polymerase activity by 50%, the studies were extended to clinica cases. Cellular NAD+ and ATP were measured in previously stored lymphocytes obtained from four patients before and after WBH; a statistically significant decrease in NAD+ was observed after WBH which quantitatively agreed with the in vitro results. Based on these results a prospective study was done in three patients; NAD+ was extracted immediately on sample collection, and the kinetics of WBH-induced NAD depletion were studied. These data, which agree quantitatively with the laboratory results, are presented.

HLA antigen expression on cultured human arterial endothelial cells

Flow cytometric analysis and cellular assays were used to determine constitutive and induced expression of class I HLA antigens and class II antigens encoded by the HLA-DR, -DQ and -DP subregions on cultured human arterial endothelial cells (HAEC) derived from transplant donors. Class I but no or minimal quantities of class II HLA antigens were found on HAEC. Prior incubation of HAEC with gamma-IFN increased class I HLA antigen expression and induced class II HLA antigen expression on HAEC. The induced expression of HLA-DQ was lower than that of HLA-DR, but both were significantly reduced in comparison to the frequency of these antigens on EBV transformed lymphoblastoid cell lines derived from the same donor. In addition, supernatants from class I and class II alloreactive clones were shown to induce class II antigen expression on HAEC. By PLT analysis, it was shown that these antigens are functionally capable of generating a lymphocyte response. In this regard, HAEC have proved to be a helpful tool in designing in vitro lymphocyte-endothelial cell studies.

Differential antigen presentation by heat-treated peripheral blood mononuclear cells and Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCL): heated EBV-LCL present alloantigen and soluble antigen but are deficient in the stimulation of autologous EBV-LCL primed T cells

Heat-treated PBM (1 hr at 45 degrees C) cannot present soluble Candida albicans antigens (CAN) or stimulate in the mixed lymphocyte culture (MLC) reaction. This is despite their continued expression of serologically defined class II MHC antigens. In contrast, heat-treated EBV-LCL present soluble CAN and stimulate allogeneic T cells in the MLC. Heated EBV-LCL stimulate strong secondary responses from allogeneic alloprimed T-cell lines in the primed lymphocyte test (PLT), while heated PBM stimulate only weak secondary allogeneic responses. To test whether this difference was due to a subtle difference in the thermal stability of the functional expression of class II MHC antigens on PBM and EBV-LCL cells, the EBV-LCL cells were heated for 1 hr at temperatures from 45 degrees C to 60 degrees C. Even after treatment at 60 degrees C, the heated EBV-LCL strongly stimulated alloreactive T cells in MLC and PLT reactions. Heated EBV-LCL are not nonspecifically mitogenic, as they do not stimulate autologous T-cell lines primed to alloantigens. However, the weak response of alloprimed T-cell lines to heated allogeneic PBM can be augmented by coculturing with autologous heated EBV-LCL, suggesting heated EBV-LCL maintain a metabolic activity necessary for allogeneic stimulation that is deficient in heated PBM. While heated EBV-LCL stimulate allogeneic alloprimed T-cell lines, they no longer stimulate autologous EBV-LCL primed T-cell lines; irradiated EBV-LCL stimulate both strongly. This suggests the involvement of a heat labile antigenic or metabolic factor in the T-cell recognition of autologous but not allogenic EBV-LCL.

Effect of UVB radiation on the biosynthesis of HLA-DR antigens

HLA-DR molecules on the surface of immunocompetent cells are thought to represent target structures for the immunomodulating effects of UV radiation during the induction of an immune response. We therefore investigated the effect of UVB radiation on the de novo synthesis of HLA-DR-gamma-chains in the cytoplasm and the expression of alpha- and beta-chains on the surface of the human lymphoblastoid B-cell line Raji. Raji cells were UVB irradiated before biochemical experiments were performed. Cells were then metabolically labeled or radioiodinated and detergent lysates immunoprecipitated using antibodies directed against the gamma- or the alpha- and beta-chain of the HLA-DR molecule. Over a wide dose range, UVB-irradiated Raji cells were shown to still express HLA-DR determinants on their surface and, even more importantly, to be capable of synthesizing HLA-DR-alpha, beta- and gamma-chains in a normal fashion. Despite this, the functional capacity of Raji cells was impaired in a dose-dependent manner. UV radiation thus seems to exert its immunomodulating effects primarily at a different level than the incriminated immune-response-associated antigens, which are expressed as recognition structures on the surface of immunocompetent cells.

Functional defect of heat-inactivated human lymphocytes in mixed-lymphocyte culture

Possible causes were examined for the inability of heat-inactivated lymphocytes to induce proliferative responses in mixed-lymphocyte cultures (MLC). Cells heated at 45 degrees C for 60 min lost greater than 90% of their capacity to stimulate in primary (1 degree) or secondary (2 degrees) MLC. This was not due to accelerated or delayed proliferation, nor to a simple quantitative loss of antigen since a 10-fold increase in stimulators or sequential addition of heated stimulators at 4-hr intervals was ineffective. Heated B lymphocytes had approximately 80% expression of HLA-DR and DQ antigens compared to unheated B cells when measured by flow cytometry using monoclonal antibodies detecting both monomorphic and polymorphic antigens. Contrary to some reports, there was no evidence of direct suppression or induction of suppression by heated stimulators or their supernatants. Reconstitution of 1 degree and 2 degrees MLC with crude MLC supernatants or more purified interleukin 1 (Il-1) or interleukin 2 (Il-2) was unsuccessful. The results indicate the heat-induced defect occurs immediately and is not due to direct or indirect suppression, insufficient amounts of Il-1 or Il-2, nor loss of polymorphic Class II HLA determinants. Heat inactivation of stimulator function may result from failure to present an "immunogenic grid" or loss of accessory molecules required in lymphocyte interactions.

Alteration of human accessory cell function by heat treatment: role of IL-1 and class II MHC antigens

Heat-treated monocytes (1 hr, 45 degrees C) cannot present soluble antigen or mitogen to purified autologous T cells. This is despite normal viability and normal expression of class II MHC antigens. They do not secrete IL-1 nor stimulate secretion of IL-2 by T cells. Addition of exogenous IL-1 or IL-2 does not, however, reconstitute the response to soluble antigen. Furthermore, even after overnight pulsing with antigen prior to heat treatment under circumstances in which the antigen is known to be appropriately processed, stimulation of T-cell proliferation still does not occur. Thus there appear to be at least two discrete lesions produced by heating: failure of IL-1 production, per se, and intrinsic failure to present previously processed antigen. It is also hypothesized that heat treatment may produce alterations in Ia molecules which specifically disallow transduction of the proliferation signal to T cells.

Presentation of Candida albicans and purified protein derivative soluble antigens by Epstein-Barr virus-transformed human lymphoblastoid B-cell lines

Cells other than the macrophage can function as antigen-presenting cells (APCs). These class II-bearing accessory cells include dendritic cells, epidermal Langerhans cells, B cells, murine B-cell tumors, and human Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCL). We investigated the ability of EBV-LCL to present two soluble antigens, Candida albicans and purified protein derivative of tuberculin (PPD). The EBV-LCL derived from B cells of two different individuals can present both antigens to bulk cultures of autologous antigen-primed peripheral blood lymphocytes. The responses of PPD-reactive T-cell clones were weaker to PPD when presented by EBV-LCL than by PBL-APCs, with some clones responding only to PPD presented by PBL-APCs. This suggests that EBV-LCL are not equivalent to PBL monocytes in APC function, and that expression of class II major histocompatibility complex antigen is not sufficient in enabling antigen-presenting capability.

Inhibition of HLA-DR antigen expression and of the allogeneic mixed leukocyte reaction by photochemical treatment

Treatment of human peripheral blood mononuclear cells with UVB light, the photosensitizing system 8-methoxypsoralen plus UVA light (PUVA), or hematoporphyrin derivative plus visible light leads to an inhibition of their stimulatory capacity in an allogeneic mixed leukocyte reaction despite unaltered expression of HLA-DR antigens when tested immediately after irradiation. However, HLA-DR positive cells disappear among mononuclear cells in the interval between 4 and 8 h after treatment with either UVB, PUVA, hematoporphyrin derivative and light, or heating to 45 degrees C. The expression of HLA-DQ, but not HLA-A,B,C, antigens, was similarly affected by these treatments. The significance of these results is discussed.

Immunologic aspects of acute cutaneous graft-versus-host disease: decreased density and antigen-presenting function of Ia+ Langerhans cells and absent antigen-presenting capacity of Ia+ keratinocytes

Cutaneous graft-versus-host disease (GVHD) provides a unique model for studying the pathogenesis of several important lymphocyte-mediated skin diseases. Morphologic studies have suggested that Ia antigen (Ia)-bearing epidermal Langerhans cells (LC) may be specific targets for destruction in these conditions. Keratinocytes synthesize and express Ia in GVHD and some other lymphocyte-mediated skin disorders; Ia+ keratinocytes, constitutively able to secrete epidermal cell-derived thymocyte activating factor (ETAF)/interleukin 1, may possess antigen-presenting capacity, thus leading to enhanced cutaneous immune responses and disease chronicity. We therefore investigated the fate of Ia+ LC, and the potential antigen-presenting capacity of Ia+ keratinocytes, in a murine model of GVHD. Lethally irradiated C3H/He (H-2k) mice developed acute cutaneous GVHD, and expressed keratinocyte Iak, 8 days after injection of BALB/c (H-2d) bone marrow and spleen cells. Immunofluorescence studies showed a progressive decrease in the density of Ia+ epidermal LC during the evolution of GVHD. This decrease was paralleled by a progressive reduction in the allostimulatory capacity of GVHD epidermal cells (EC) in the allogeneic EC-lymphocyte reaction (ELR). The fall in the density of Ia+ LC, and in EC allostimulatory capacity in both primary and secondary ELRs, was consistently greater in GVHD mice than in mice treated only with x-irradiation. The allostimulatory capacity of GVHD and x-irradiated EC could not be restored by addition of indomethacin or exogenous ETAF to ELR cultures. The decreased allostimulatory capacity was not the result of inhibition of the ELR, since EC from GVHD and x-irradiated mice did not cause suppression when added to control ELR cultures. The capacity of EC to present ovalbumin, purified protein derivative of tuberculin, 2,4,6-trinitrobenzenesulfonic acid coupled to EC, and native cytochrome c (CYTc) to antigen-specific T-cell lines, clones, or hybridomas was reduced in x-irradiated mice and markedly decreased in GVHD mice. The capacity of EC from x-irradiated and GVHD mice to present CYTc fragment 81-104, which does not require further processing or catabolism by accessory cells, was similarly decreased. Taken together, the results indicate that: the function of LC is markedly and progressively impaired in acute GVHD; LC function is also decreased, but to a lesser extent, following x-irradiation alone; and Ia+ keratinocytes from lethally irradiated mice undergoing GVHD do not exhibit antigen-presenting capacity.

The alloimmunogenicity of heated blood and lymphoid cells

Murine lymph node cells heated to 45 degrees C for 1 h or 56 degrees C for 15 min lost their ability to provoke a primary cytotoxic alloantibody response, though they were able to provoke a secondary response in animals primed with normal lymph node cells two months previously. The primary immunogenicity of whole blood and spleen cell preparations was destroyed by 56 degrees C but not by 45 degrees C treatment. Treatment of spleen cells with 45 degrees C heat, and ammonium chloride to remove red cells, destroyed their immunogenicity, whereas ammonium chloride treatment alone did not, suggesting that the red cells were the immunogenic component of heated spleen cells and, by implication, of blood. Further evidence for a difference in the immunogenicity of 45 degrees C heated blood and normal blood was provided by the finding that heated blood did not prime for a response to 45 degrees C lymph node cells given two months later. Preliminary investigations of the tolerogenicity of heated cells were unsuccessful, indicating, in view of the published data, that the precise protocol for tolerance induction is very critical.

Differential stimulatory requirements and regulation of naive and primed human lymphocytes

In these investigations, human lymphocytes primed in vitro in MLR have been employed as a model for human memory cells and have been compared to naive lymphocytes from the same donor. Both the stimulatory requirements and the regulation of these cells were found to differ significantly. The dose of stimulators giving a maximal primary (I) response was less than 10% the dose of restimulating cells giving a maximal secondary (II) response. II responses were further found to be inversely related to the original I response. This was associated with at least two separate regulatory phenomena. Suppressor cell induction was enhanced at high priming doses while memory cell precursors were preferentially stimulated at very low priming doses. Priming of memory cells could also be demonstrated to occur in the absence of any detectable I proliferation by utilizing platelets or heat treated stimulators. Memory cells were also a much more resistant than naive cells to both alloantigen induced suppressor cells and to culture activated monocyte suppressor cells. This in vitro model suggests that the human I and II responses to alloantigen have both distinct triggering requirements and differential sensitivity to regulatory cells. It is suggested that preferential formation of memory cells under conditions that require no proliferation and which are suboptimal for suppressor cell generation and the acquired resistance of memory cells to down regulation by suppressor cells may contribute to the poor graft prognosis of sensitized renal transplant patients.