The uptake and efflux of doxorubicin by a sensitive human bladder cancer cell line and its doxorubicin-resistant subline

The uptake and efflux of doxorubicin (Dox) were investigated in a human bladder cancer cell line (UM-UC-6) and in a multi-drug resistant (mdr) subline (UM-UC-6Dox). Unlike previous reports, the initial uptake kinetics of Dox, and its accumulation and retention to steady-state were modelled mathematically. Cells were incubated with Dox and the amount of Dox in the cellular and medium phases was measured by a specific HPLC method. When monitored for 1 min from 0.02 microM to 25 microM Dox, the uptake was very rapid but was significantly faster in the resistant cell line. The initial rate of uptake at t = 0 followed Michaelis-Menten kinetics yielding Vmax values (the maximal rate of uptake) of 15.0 +/- 1.7 and 12.9 +/- 1.2 nmol/10(6)/min and Km (rate at Vmax/2) of 25.2 +/- 4.7 and 16.4 +/- 2.9 microM for UM-UC-6 and UM-UC-6Dox, respectively. There was no metabolism of Dox by keto-reduction or reductive hydrolysis. At 1.0 microM the uptake of Dox to steady-state was biexponential but there was no difference in total cellular Dox concentration between the two cell lines at equilibrium. A 3 compartment sequential closed model was fitted yielding significantly different values for the intercompartmental and hybrid rate constants, indicating altered intracellular distribution in resistant cells. Verapamil (10 microM), trifluoperazine (10 microM) or Tween 80 (0.005%) had no effect on the uptake or efflux of Dox. The UM-UC-6Dox line appeared to show atypical mdr characteristics since net drug accumulation was not lowered and classic P-glycoprotein inhibitors were not effective. The primary mechanism of Dox resistance is not enhanced metabolism or lowered intracellular concentrations.

Comparison of antigen expression on normal urothelial cells in tissue section and tissue culture

Antigenic characterization of urothelial cells cultured from normal adult ureter was performed. These cells were cultured using a simplified isolation and culture technique and a commercially available serum-free medium. The cells growing in these cultures had epithelioid morphology and normal quantities of DNA. The antigen expression on these cultured normal urothelial cells was evaluated using a panel of monoclonal antibodies: 5G6.4, AN43, URO-5, anti-keratin and anti-blood group antibodies, and 425 (anti-epidermal growth factor receptor). Lower levels of anti-A and AN43 binding on cultured cells were observed than are seen on urothelial cells in sections of normal ureter, while the binding of anti-blood group H, 5G6.4, and URO-5 was unchanged. Binding of anti-epidermal growth factor receptor antibody 425 was improved if the cells were grown in medium lacking epidermal growth factor. These results confirm the urothelial origin of these cultured urothelial cells but indicate that some antigenic differences between cultured normal urothelial cells and urothelial cells in situ in the normal ureter exist.

Products of cells from gliomas: VIII. Multiple-well immunoperoxidase assay of immunoreactivity of primary hybridoma supernatants with human glioma and brain tissue and cultured glioma cells

To test the feasibility of primary screening of hybridoma supernatants against human glioma tissue, over 5000 combinations of hybridoma supernatants with glioma tissue, cultured glioma cells, and normal central neural tissue were screened with a new multiple-well (M-well) screening system. This is an immunoperoxidase assay system with visual endpoints for screening 20-30 hybridoma supernatants per single microscope slide. There were extensive differences between specificities to tissue and to cultured glioma cells when both were screened with M-wells and when cultured cells were screened with standard semi-automated fluorescence. Primary M-well screening with glioma tissue detected seven hybridoma supernatants that specifically identified parenchymal cells of glioma tissue and that were not detected with cultured cells. Immunoreactivities of individual supernatants for vascular components (nine supernatants), necrosis (five supernatants), and nuclei (three supernatants) were detected. Other supernatants bound multiple sites on glioma tissue and/or subpopulations of neurons and glia of normal tissue. The results show that primary screening with glioma tissue detects a number of different specificities of hybridoma supernatants to gliomas not detected by conventional screening with cultured cells. These are potentially applicable to diagnosis and therapy.

Lymphoscintigraphy in melanoma: initial evaluation of a low protein dose monoclonal antibody cocktail

A low protein dose (73 +/- 10 micrograms total) 131I-labeled monoclonal antibody cocktail made of equal microgram quantities of 225.28S (IgG2a) and 763.24T (IgG1) murine monoclonal antibodies, which bind additively to a high molecular weight antigen of melanoma, was evaluated as a lymphoscintigraphic agent in 17 patients with intermediate to thick (mean Breslow depth, 3.39 +/- 0.64 mm) melanomas or clinical Stage II disease scheduled for nodal dissection. Eleven of the patients were clinically Stage I while 6 were clinically Stage II. 131I antibody cocktail, 258 +/- 10 microCi, was administered s.c. at the site of the primary melanoma or its scar following surgical removal. In eight patients, 63 +/- 8 microCi of 125I nonspecific normal sheep IgG was coadministered s.c. Gamma camera imaging was conducted beginning immediately after and continuing for several days following injection. Surgical resection, weighing, and gamma counting of the draining lymph nodes were undertaken in all patients. On gamma scans, early nodal uptake of antibody was most pronounced and of longest duration in the tumor pathologically positive patients (5 of 7 had visible nodal uptake, 4 of 7 visually stable or rising with time), with the t 1/2 of nodal clearance by gamma scan significantly (P less than 0.05) longer than in the negative patients in whom 4 of 10 showed some, although generally transient (0 of 10 stable or rising), nodal uptake. Scans were not easily interpretable when the injection site was very near the draining nodal group, in part due to the detection of scatter activity from the injection site. In several instances the scan was correct and the clinical examination was incorrect as regards nodal disease. Quantitative analysis of the surgically excised draining nodes showed significantly (P less than 0.001) more 131I anti-melanoma antibody uptake in the 21 tumor-involved nodes [0.01217% injected dose (ID)/node median] than in the 512 tumor-negative nodes (0.00051% ID/node median). Median percentage ID/g of anti-melanoma antibody in tumor-involved nodes was significantly greater (P less than 0.01) than in tumor-negative nodes (0.01984 versus 0.003215% ID/g). 125I-labeled nonspecific antibody did not accumulate significantly more in the tumor-involved nodes on a per node or per g basis in the 283 of 533 nodes studied using the dual-label approach (0.0036 versus 0.00092% ID/g). These data demonstrate that by external imaging and by tissue counting that a radiolabeled anti-melanoma monoclonal antibody cocktail can specifically accumulate to melanoma-involved lymph nodes following s.c. administration.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification by monoclonal antibodies of an antigen shed by human bladder cancer cells

The reactivities of two anti-bladder cancer monoclonal antibodies, AN43 and BB369, were characterized. AN43 and BB369 reacted with a majority (greater than 50%) of bladder cancer tissue sections tested by immunoperoxidase staining. When tested against a panel of 27 normal human tissues, AN43 and BB369 reacted only with urothelium and stomach. AN43 and BB369 showed identical binding patterns and competed for binding on bladder cancer cells, suggesting that the two antibodies react with identical or spatially close epitopes. Bound BB369 antibody was rapidly shed from the surface of viable UM-UC-9 human bladder cancer cells. The antigen was found in spent tissue culture medium from the UM-UC-9 human bladder cancer cell line. AN43 and BB369 define a shed bladder tumor-associated antigen with limited distribution on normal tissues. The antigen is different from bladder tumor-associated antigens defined by other monoclonal antibodies and may be useful for the diagnosis and follow-up of patients with bladder cancer.

Improved radiolabeled monoclonal antibody uptake by lavage of intraperitoneal carcinomatosis in mice

The effect of peritoneal lavage with saline on tumor and systemic uptake of intraperitoneally administered tumor-specific (131I-5G6.4) and nonspecific (125I-UPC-10) radiolabeled monoclonal antibodies was evaluated in a nude mouse model of human intraperitoneal ovarian carcinomatosis (IP3 model). Peritoneal lavage at 2 or 6 hr postintraperitoneal antibody injection significantly improves intraperitoneal tumor/nontumor uptake ratios of specific antibody apparently by limiting systemic exposure to antibody. This enhancement tends to be more dramatic if lavage is performed within 2 hr, rather than 6 hr, of intraperitoneal antibody administration, though both times result in significant improvements in target/background ratios over no lavage. Twenty-four-hour tumor/nontumor ratios for specific antibody 5G6.4 generally are 1.5-fourfold higher following lavage than those achieved in control animals, without decreasing absolute tumor uptake of specific radiolabeled antibody. By contrast, nonspecific antibody UPC-10 binding is lower in tumor and normal tissues following lavage, with no lavage-induced improvement in tumor/nontumor ratios seen. Peritoneal lavage is a simple method to allow for specific antibody binding to accessible intraperitoneal tumors yet to limit systemic exposure thus increasing the therapeutic margin. This method may have considerable applicability in the enhancement of intraperitoneal immunoconjugate delivery to intraperitoneal tumors.

Radiolabeled antibodies, albumin and antimony sulfide colloid: a comparison as lymphoscintigraphic agents

The kinetics of lymph node and systemic uptake of members of three different classes of lymphoscintigraphic agents were studied in normal laboratory rats. 99mTc antimony trisulfide colloid (TcSbC), 99mTc human serum albumin (TcHSA), 125I 5G6.4 (a murine IgG2ak monoclonal antibody), 125I 763.24T (a murine IgG1), and 125I FT166 ( a murine IgM monoclonal) all current or potential lymphoscintigraphic agents, were injected subcutaneously into the hind foot pads of healthy rats. Ipsilateral and contralateral popliteal lymph nodes were sampled up to 4 h post-injection. Subcutaneous injection resulted in far higher nodal uptake for all agents than i.v. delivery with ipsilateral popliteal node/blood ratios 1 h postsubcutaneous injection of: for TcSbC (1900) greater than 125I IgM (497) greater than TcHSA (72) greater than 125I Intact IgG2a or 125I IgG1 at approximately 10. Thus, while all agents achieve popliteal node/blood ratios far greater than unity, TcSbc has the greatest absolute and relative nodal accumulation, greater than the 125I IgM monoclonal antibody and TcHSA. Uptake of the intact 125I IgG antibodies is lowest. These data suggest that TcSbC in particular, as well as TcHSA and IgM may be most useful as non-specific nodel imaging agents, while the lower background activity of the IgGs may make targeting specific antigen in nodes more feasible.

The intraperitoneal delivery of radiolabeled monoclonal antibodies: studies on the regional delivery advantage

The i.p. delivery of murine monoclonal antibody was compared with i.v. delivery in normal mice and rats, in normal nude mice and in those with i.p. human ovarian carcinoma xenografts. In normal rats, all classes of antibodies and antibody fragments evaluated were cleared from the peritoneal cavity at comparable rates. The regional delivery (Rd1) advantage to the peritoneal cavity following i.p. delivery was thus most dependent on the rate of clearance of the antibody or fragment from the blood stream. Determining the exact i.p. delivery advantage was problematic due to the difficulty in reliably obtaining peritoneal fluid later than 9-10 h after i.p. injection in normal animals. During the first 9 h following i.p. injection, the Rd(0-9/0-9) was, for a murine IgG2ak Fab greater than F(ab')2 greater than IgG (at 13.6 greater than 10 greater than 7.9). Two murine IgMs evaluated differed in Rd(0-9) at 27.1 and 9.2 respectively. When blood levels were extrapolated to infinity, these Rd (0-9/affinity) values were considerably lower with the Fab having the highest Rd at 4.67. The i.p. Rd advantage was almost solely due to the i.p. antibody levels seen in the first 24 h after injection, as after that time, blood levels become comparable to those seen following i.v. injection. Normal tissues obtained at sacrifice 5-7 days after i.p. injection. Normal tissues obtained at sacrifice 5-7 days after i.p. or i.v. injection in rats showed comparable levels of radioantibody activity, whether the injection was i.p. or i.v. (except for higher diaphragmatic levels following i.p. delivery). In nude mice with i.p. human-derived ovarian tumors, intact IgG clearance from the peritoneal cavity to the blood was considerably slower than in normal animals, and early i.p. tumor uptake of specific antibody was significantly higher than that following i.v. antibody delivery. With higher early tumor uptake and lower systemic exposure, early tumor/nontumor ratios were significantly greater than those for i.v. delivery, though not beyond 48 h after i.p. injection. This study demonstrates the pharmacokinetic rationale for i.p. monoclonal antibody delivery, especially for agents cleared rapidly from the blood, such as antibody fragments. In addition, definite i.p. delivery benefit for antibody specific to i.p. tumors in the i.p. ovarian cancer system was shown soon after injection. These data regarding i.p. antibody delivery should be useful in rationally planning diagnostic and therapeutic studies involving the i.p. delivery of unmodified and immunoconjugated monoclonal antibodies.

Kinetics of interstitially administered monoclonal antibodies for purposes of lymphoscintigraphy

The clearance rates of radiolabeled murine monoclonal intact IgG, F(ab')2 Fab and of an IgM following subcutaneous administration were evaluated in normal mice and rats using nuclear imaging and counting techniques. These studies suggest no significant difference in clearance rate exists between intact IgG and its F(ab')2 fragment, and little difference between these moieties and intact IgM. Fab is cleared considerably faster than the others, however. While significant differences in clearance rates exist, the magnitude of the differences are not as large as those following intravenous injection particularly when ambulation by the animal is allowed. When ambulation is allowed, clearance rates of all classes and fragments are accelerated and quite similar. Injection into the subcutaneous tissues of the footpad results in consistently faster clearance than an injection into the subcutaneous tissues of the abdomen. Ambulation considerably increased the clearance of antibodies, presumably by increasing lymph flow. These studies imply that the choice of intact antibody versus fragments for kinetic reasons may be less critical (particularly if ambulation is allowed) by the subcutaneous as compared with the intravenous delivery route. This kinetic information should be useful in designing imaging protocols with radiolabeled antibodies administered subcutaneously for purposes of imaging disease processes involving the lymphatics.

A semi-automated fluorescent (SAF) assay using viable, whole cells for screening hybridoma supernatants

In the production of monoclonal antibodies, a rapid, sensitive, accurate assay is needed for the critical step of screening. We report the modification of an assay using viable whole cells for screening hybridoma supernatants. The modified assay uses fluorescent second antibodies for detection and has been adapted to an instrument capable of automating a number of assay steps. The modified assay is compared to a dot radioimmunoassay developed and used in our laboratory. The fluorescence assay is highly sensitive but shows more background effect, especially in samples with high protein content, such as ascites. The automated fluorescence assay is very rapid, capable of completing an assay in less than 90 min, and can be performed with minimal operator involvement. The assay was performed successfully with several different antibodies and cell types. This screening procedure should be especially useful for laboratories with large numbers of fusions to evaluate.

Monoclonal antibody (5G6.4) against ovarian carcinoma shows inhibition of in vitro colony formation

Monoclonal antibodies (MAbs) have the potential for diagnosis and therapy of cancer, 5G6.4 is a MAb of the IgG2a class which was produced by immunization of BALB/c mice with human ovarian carcinoma (Ov Ca) cells. To further characterize 5G6.4, its effect on cell growth was tested using a human Ov Ca cell line established in our laboratory. A clonogenic assay was set up in 48-well plates in a double agar system. The cells were plated and 5G6.4 was added at different concentrations. Control plates consisted of cells with media without MAb. Negative control plates were also prepared using the same concentrations of an isotype-matched antimelanoma MAb, 225.28s. Colony formation (CF) was reduced to 50% or less of control with increasing amounts of 5G6.4 up to 50 micrograms/ml. Although CF was still depressed at concentrations above 50 micrograms/ml, the inhibition did not follow a directly proportional line; instead, it followed a bell-shaped curve. Plates with the control MAb, 225.28s, did not show this response. Similar results were obtained with cells from malignant Ov Ca ascites in the same clonogenic assay. Our study suggests that in the evaluation of the in vitro effect of MAb on growth, the concentration of MAb is crucial and may not show a linear response and that 5G6.4 may have a direct therapeutic effect by blocking the growth of Ov Ca cells. 5G6.4 is presently under study for therapy in an animal model.

Detection of SSEA-1 on human renal tumors

Stage-specific embryonic antigen-1 (SSEA-1) was localized on paraffin embedded, formalin fixed specimens of human renal tumors by immunoperoxidase staining using a monoclonal antibody. Of 19 renal cell carcinoma (RCC) samples tested, 12 were positive for SSEA-1; SSEA-1 was also found on distinct elements in two samples of Wilms' tumor. No correlation was found between expression of SSEA-1, and RCC morphology or pattern of growth. Because SSEA-1 is found on proximal tubules in the normal kidney, these results support the hypothesis that RCC arises from the cells of the proximal tubule. Furthermore, since greater than 60% of the RCCs examined expressed SSEA-1, this antigen may prove to be a useful target for immunolocation or therapy of metastatic RCC.

High-dose, unlabeled, nonspecific antibody pretreatment: influence on specific antibody localization to human melanoma xenografts

Nonspecific uptake of radiolabeled monoclonal antibodies in normal tissues is a significant problem for tumor imaging. A potential means of decreasing nonspecific antibody binding is to "blockade" nonspecific antibody binding sites by predosing with cold, nonspecific isotype-matched antibody, before injecting specific antibody. Nontumor-specific murine monoclonal antibody LK2H10 (IgG1) or Ab-1 (IgG2a) was given i.v. at doses of 0 to 3.5 mg to nude mice with xenografts of human melanoma. These mice were then given i.v. 4 micrograms of 131I anti-high molecular weight antigen of melanoma (HMWMAA) monoclonal antibody 763.24T (IgG1) or 225.28S (IgG2a), respectively. These mice were also given a tracer dose of 125I LK2H10 or Ab-1, respectively. Specific tumor uptake of anti-HMWMAA antibodies was see in all cases. No drop in tumor or nontumor uptake was demonstrated for either of the tumor-specific or nonspecific monoclonal antibodies due to nonspecific monoclonal antibody pretreatment. These data suggest that high doses of isotype-matched unlabeled nonspecific monoclonal antibody given before 131I tumor-specific monoclonal antibody, will not enhance tumor imaging.

Products of cells cultured from gliomas. V. Cytology and morphometry of two cell types cultured from glioma

Explants of cells of a human glioma were evaluated with the nuclear fluorochrome 4',6-diamidino-2-phenylindole, by phase-contrast illumination, and by Giemsa staining correlated with double immunofluorescence for glial fibrillary acidic protein (GFAP) and fibronectin (FN). FN-positive (FN+) cells lacked GFAP detectable by immunofluorescence. Their mean nuclear-to-cytoplasmic ratio was large (0.192). Actual mean areas of nuclei (1,252 microns2) and cytoplasm (8,376 microns2) of FN+ cells compared with mean areas of fibroblasts suggested that the high nuclear-to-cytoplasmic ratio of FN+ cells was due to their microscopically evident reduced cytoplasmic spreading rather than to larger nuclei. Some FN+ cells showed marked variation in nuclear and nucleolar size and shape. Others had abnormal mitoses or hyperchromatic nuclei. GFAP-positive (GFAP+) cells lacked FN detectable by immunofluorescence. GFAP+ cells were smaller and less round than FN+ cells. Their usual location was growing on a layer of FN+ cells. The mean nuclear-to-cytoplasmic ratio (0.245) of GFAP+ cells was the highest in the study, surpassing the ratio of the continuous glioma line LM (0.176). Mean areas of nuclei (289 microns2) and of cytoplasm (1,350 microns2) of GFAP+ cells suggested that their high nuclear-to-cytoplasmic ratio was due to their microscopically evident reduced cytoplasmic spreading. Reduced spreading was associated with extension of long, thin cytoplasmic processes. The majority of GFAP+ cells showed marked cytoplasmic basophilia, nuclear hyperchromasia, and clumped chromatin. Features observed in both FN+ and GFAP+ cells from this high-grade astrocytoma are features associated with malignant transformation in more thoroughly studied tumor systems.

Effect of herpesvirus infections on T-lymphocyte subpopulations and blastogenic responses in renal transplant recipients receiving cyclosporine

The immunosuppressive effects of three herpesviruses--cytomegalovirus (CMV), Epstein-Barr virus (EBV), and herpes simplex virus (HSV)--were assessed in 29 renal transplant recipients treated with cyclosporine and prednisone. The ratios of Leu 3-positive ("helper-inducer") to Leu 2-positive ("suppressor-cytotoxic") T lymphocytes in peripheral blood were only moderately and transiently decreased during primary CMV infection, with or without concurrent reactivated EBV and HSV infections. This effect was due to an increase in absolute numbers of Leu 2-phenotypic and decrease in Leu 3-phenotypic T cells and was associated with symptomatic viral illness. Reactivated CMV infection alone or together with reactivated EBV and HSV infections resulted in less significant alterations in T-cell subsets than did primary CMV infection. Lymphocyte blastogenesis was not significantly altered during the herpesvirus infections. The data suggest that cyclosporine treatment inhibits the activation of suppressor cells and depression of cellular immune function that have been associated with herpesvirus infections in renal transplant recipients undergoing conventional immunotherapy.

The influence of monoclonal antibody dose on tumor uptake of radiolabeled antibody

The impact of antibody protein dose on tumor accumulation of radiolabeled monoclonal antibody was studied in nude mice with xenografts of human melanomas. 225.28S, a murine monoclonal antibody reactive with a high-molecular weight antigen of melanoma, was radiolabeled with I-125 and administered intraperitoneally to nude mice with human melanoma xenografts. Three days later, the animals were sacrificed, and tumor and normal tissue uptake of I-125 antibody was determined. At doses of 6.25, 62.5, 625 and 1875 ug of monoclonal antibody, there were no significant differences in percent of injected dose reaching the tumor/g of tumor or in the non-tumor uptakes achieved. These findings indicate that in the melanoma system, antibody dose is not a critical determinant of tumor uptake, and additionally indicate that low doses of antibody protein are appropriate for studies involving radioiodinated antibody localization.

A method of membrane preparation for immunoassay

Membranes prepared from a variety of solid tissues were used as solid-phase antigens for ELISA or RIA after fixation onto polylysine-primed 96-well plates. The preservation of antigens in these membrane preparations was tested by reactivity in ELISA using 2 monoclonal antibodies: W6/32, which recognizes an HLA framework antigen (a protein antigen) and anti-SSEA-1, directed to a carbohydrate antigen carried on glycoproteins. Levels of antigen deposition and usefulness as solid-phase antigens were assessed for ELISA as compared to RIA. Coated plates may be frozen for many months with preservation of antigenic activity. This method is relatively simple, rapid, and is useful for preparation of tissue antigens for immunoassay, especially for screening monoclonal antibodies.

The relative roles of MHC and non-MHC genes in heart and skin allograft survival

Although the role of the major histocompatibility complex (MHC) of the rat (RT1) in graft rejection has been established, the role of non-RT1 genes is not well understood. To investigate the influence of MHC and non-MHC genes in graft rejection, various combinations of congenic and inbred strains of rats were used as donors and recipients of skin grafts and perfused abdominal heart grafts. In addition, hemagglutinating and cytotoxic antibody responses were evaluated to assess loci that were serologically active in transplantation. Our results demonstrate that: (1) RT1 antigens are the most important determinant in heart and skin rejection; (2) antigens controlled by non-MHC genes also play a major role in rejection because they cause disparate heart grafts to be rejected by day 18 and skin grafts by day 26; (3) RT2 cell antigens alone do not cause graft rejection; and (4) allogeneic differences at the RT1, RT2, RT3, and RT6 loci elicit an antibody response in heart transplantation.

Comparison of antigens in the rat MHC that act as CML determinants

We have examined a variety of RT1 haplotypes using congenic strains of rats to investigate the comparative relationships among MHC antigens that have been reported to serve as cell-mediated lympholysis (CML) targets. These studies demonstrate that: (1) RT1.A antigens can act as CML determinants, and in some haplotypes they display identical serological and CML reaction patterns; (2) in some donor-recipient strain combinations RT1.A antigens may act as immunodominant determinants, preventing the generation of effectors capable of recognizing other antigens, and (3) a portion of the antigenic determinants that define the anti-CT CML response can be mapped to the same region of the rat MHC as the RT1.E locus.

CML characterization of a product of a second class I locus in the rat MHC

In the rat, genes that control the expression of target antigens detected by cell-mediated lympholysis (CML) are present in the major histocompatibility complex (MHC). The relationship of these loci, CT and Ag-L, to each other and to other loci within the MHC is unknown. In this report, we demonstrate the existence of a CML target antigen in the (DA X BN)F1 anti-DA.1I(BI) strain combination. The gene coding for this antigen is linked to the RT1 complex as indicated by the CML reactivity of targets from backcross and congenic animals. Inhibition studies demonstrated that this antigen has the widespread tissue distribution characteristic of class I antigens, and the gene coding for this CML antigen maps coincident with the RT1.E class I locus as indicated by the lysis of targets from the recombinant strains r10 and r11. The CML can be blocked by antisera directed against a product of the RT1.E locus. The locus controlling this CML reactivity, like CT and Ag-L, has been separated from RT1.A by recombination; unlike CT and Ag-L, the produce of this CML locus appears to be identical with an RT1.E allelic product that has been serologically identified and biochemically characterized.

Gene order in the major histocompatibility complex of the rat

The loci in the major histocompatibility complex (MHC) of the rat which code for class I and class II antigens--RT1.A and RT1.B, respectively--have previously been separated by laboratory-derived recombinants and by observations in inbred and wild rats. Closely linked to the MHC is the growth and reproduction complex (Grc) which contains genes influencing body size (dw3) and fertility (ft). These phenotypic markers were used in this study to orient the A and B loci of the MHC. Two recombinants were used for mapping. The BIL(R1) animal is a recombinant between the MHC and Grc, and it carries the haplotype RT1.AlBlGrc+. The r10 animal is an intra-MHC recombinant, and it has the haplotype RT1.AnB1Grc. These recombinants were characterized serologically, by mixed lymphocyte reactivity, by immune responsiveness to poly (Glu52Lys33Tyr15) and by the presence of the dw-3 gene. The data demonstrate that the gene order of the loci is: dw-3--RT1.B--RT1.A.

Expression of HLA-B12 on platelets, on lymphocytes and in serum: a quantitative study

Expression of the antigen HLA-B12 on platelets, on lymphocytes and in serum of normal subjects was studied using several quantitative techniques. HLA-B12 was found to be expressed on platelets from each of 25 heterozygous HLA-B12-positive donors in amounts varying about 35-fold from weakest to strongest. Expression of B12 on platelets was enhanced in the presence of the first locus antigen A11, but decreased in the presence of A2, A3, and Aw28. The antigen was expressed in equal strength on lymphocytes sampled from the same donor population. Serum content of B12 assayed in five subjects was found to be roughly proportional to the expression of that antigen on platelets. Expression of B12 on platelets is under genetic control but the precise mechanism of inheritance has not yet been defined. The applicability of these findings to transfusion of single donor platelets to alloimmunized patients is under investigation.