A novel frameshift mutation in RHAG leads to Rhnull phenotype in a Chinese individual

BACKGROUND

We recently encountered a Rhnull phenotype proband within one family in the Chinese population. Rhnull is a rare autosomal recessive disorder characterized by the absence of the Rh antigens on the erythrocyte membrane, resulting in chronic hemolytic anemia. This study described the serological and molecular analysis of a Chinese Rhnull proband and his immediate family.

METHODS

Red blood cells antigen phenotyping and antibody screening/identification were conducted. RHD, RHCE, and RHAG were analyzed using genomic DNA by polymerase chain reaction and sequence analysis.

RESULTS

Serologic tests showed a D-C-E-c-e- phenotype in the proband associated with the suspicion of anti-Rh29 (titer 16). Molecular analyses showed a new mutation (c.406dupA) in exon 3 of RHAG. This duplication introduced a reading frameshift (p.Thr136AsnfsTer21). The RHAG mutation was found in the homozygous state for the proband and heterozygous state for his parents.

CONCLUSION

We identified a novel RHAG mutation resulting in the Rhnull phenotype of the regulator type. Inheritance of the novel allele was shown by family study.

Integrase Defective Lentiviral Vector Promoter Impacts Transgene Expression in Target Cells and Magnitude of Vector-Induced Immune Responses

Integrase defective lentiviral vectors (IDLVs) are a promising vaccine delivery platform given their ability to induce high magnitude and durable antigen-specific immune responses. IDLVs based on the simian immunodeficiency virus (SIV) are significantly more efficient at transducing human and simian dendritic cells (DCs) compared to HIV-based vectors, resulting in a higher expansion of antigen-specific CD8+ T cells. Additionally, IDLV persistence and continuous antigen expression in muscle cells at the injection site contributes to the durability of the vaccine-induced immune responses. Here, to further optimize transgene expression levels in both DCs and muscle cells, we generated ten novel lentiviral vectors (LVs) expressing green fluorescent protein (GFP) under different hybrid promoters. Our data show that three of the tested hybrid promoters resulted in the highest transgene expression levels in mouse DCs, monkey DCs and monkey muscle cells. We then used the three LVs with the highest in vitro transgene expression levels to immunize BALB/c mice and observed high magnitude T cell responses at 3 months post-prime. Our study demonstrates that the choice of the vector promoter influences antigen expression levels in target cells and the ensuing magnitude of T cell responses in vivo.

Evaluation of PD-L1 antigen expression using immunohistochemistry technique in medullary thyroid carcinoma samples

BACKGROUND

Markers related to the mechanism of tumoral cell escape from the immune system have received more attention. The PD-L1 molecule encoded by the "CD274" gene binds to T lymphocytes and can inhibit these cells. Therefore, increasing the expression of this marker on inflammatory or tumor cells can indicate tumor progression invasiveness and long-term consequences. The present study aimed to determine the expression of the PD-L1 marker in thyroid medullary tumors and to evaluate its role in predicting long-term outcomes after cancer.

METHODS

This retrospective longitudinal study was performed on pathology samples of patients with medullary thyroid carcinoma referred to the Cancer Institute of Imam Khomeini Hospital from 2015 to 2020. Slides related to medullary thyroid tumors were examined. A tissue microarray was used to evaluate the immunohistochemistry of PD-L1. Patients were followed up to assess the occurrence of recurrence. Out of 207 patients evaluated in the present study, histopathological information of 144 patients was available.

RESULTS

The expression rate of PD-L1 in our community was 14.6% in lymphocyte cells, 35.4% in tumor cells, and 12.5% in both cells. The presence of metastasis at the time of diagnosis was reported in 35 cases (72.9%), and the occurrence of tumor recurrence was reported in 38 cases (79.2%). There was no relationship between the expression of this marker and the sex and age of patients. In addition, PD-L1 expression was unrelated to the two main characteristics of this cancer, namely tumor size and its focality. The presentation of tumor PD (L1) (but not lymphocytic) was a prognostic marker for synchronous metastasis at cancer diagnosis but could not predict tumor recurrence.

CONCLUSION

PD-L1 tumor marker expression is predictable in 14.6% of lymphocyte cells, 35.4% of tumor cells, and 12.5% in the selected Iranian population with medullary thyroid cancer. The expression of this marker is not related to the morphological characteristics of the tumor, such as tumor size or focality.

A comparison and review of the flow cytometric findings in classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, T cell/histiocyte rich large B cell lymphoma, and primary mediastinal large B cell lymphoma

The "Hodgkin-like" lymphomas including classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, T cell/histiocyte rich large B cell lymphoma, and primary mediastinal large B cell lymphoma have been shown to be pathobiologically related. With the exception of primary mediastinal large B cell lymphoma, these lymphomas have similar morphologic growth patterns with occasional neoplastic cells within a prominent reactive cell background. Historically, distinguishing these entities was difficult by flow cytometry; however, over the past 15 years, our laboratory has developed antibody-fluorochrome combinations capable of accurately distinguishing these entities by their immunoprofile. Additionally, an algorithmic approach based on characterization of the background reactive B-cell and T-cell populations can aid in narrowing the differential diagnosis. This review summarizes both the morphologic and immunophenotypic features and the current flow cytometric insights of the neoplastic and reactive populations found in this unique subset of lymphomas.

Biological Characterization of Hepatitis B virus Genotypes: Their Role in Viral Replication and Antigen Expression

Hepatitis B virus (HBV) inter-host evolution has resulted in genomic diversification reflected in the existence of nine genotypes (A-I) and numerous subgenotypes. There is growing evidence that genotypes influence HBV natural history, clinical outcomes, and treatment response. However, the biological characteristics underlying these differences have not yet been established. By transfecting HuH-7 cells with unit-length constructs of genotypes A2, B2, C1, D1, and F1b, we identified major differences in HBV replicative capacity and antigen expression across genotypes. Genotypes B2 and F1b showed a 2-fold increase in cccDNA levels compared to the other genotypes (p<0.005). Genotype A2 expressed the lowest pgRNA levels, with a 70-fold decrease in relation to the other genotypes (p<0.0001), while genotype B2 showed the lowest Precore RNA levels, with a 100-fold reduction compared to genotype A2 (p<0.0001). The highest intracellular HBV DNA levels were observed for genotype B2 and the lowest for genotypes A2 and C1 (p<0.0001). Regarding antigen expression, genotype F1b secreted the highest HBsAg levels and genotype D1 the lowest (p<0.0001), while genotypes A2 and B2 showed the highest intracellular HBsAg levels (p<0.0001). Interestingly, genotype C1 secreted the highest HBeAg levels, while genotype A2 showed the highest intracellular levels (p<0.0001). Finally, the analysis of the intra/extracellular antigen ratios revealed that most genotypes retained intracellularly 5-20% of the antigens, except the genotype A2 that retained 50% of the total expressed antigens. In conclusion, this study provides new insights into the biological characteristics of HBV genotypes, being the first study to comparatively analyze European (A and D) and Asian (B and C) genotypes with the Latin American (F) genotype. The differences in HBV replication and antigen expression might contribute to understand the differential role of genotypes in pathogenesis.

The influence of fixation of biological samples on cell count and marker expression stability in flow cytometric analyses

The most common applications of flow cytometry (FC) include diagnostics of haemato-oncological disorders, based on analysis of bone marrow, peripheral blood (PB), or cerebrospinal fluid (CSF) samples. A proper diagnostic process requires standardisation in setting the optimal time frame between material collection and the assay. Unfortunately, this might be difficult to achieve in daily practice due to unintended shipment delays, which might compromise large-scale multicentre studies. Thus, material fixation should be considered as a solution. The most widely used fixative agents are: paraformaldehyde, TransFix^®, Cyto-Chex^®, and serum-containing media. In this review, we attempted to summarise the literature data on the influence of sample storage under different temperatures and times combined with different fixation conditions on the cell count and marker expression levels. Based on the findings of several extensive studies employing fixed PB samples, it can be concluded that the performance of particular fixative greatly depends on the analysed marker and specific PB cell population expressing a given antigen. Preservation of absolute cell count was usually better in Cyto-Chex^®-fixed PB samples, whereas TransFix^® tended to better stabilise marker expression levels. CSF-based studies reveal that both serum-containing media and TransFix^® can prevent cellular loss and enhance FC-based detection of leptomeningeal localisations of haematological malignancies, the latter being more available and having longer shelf-life. As both cell count and marker expression level are the main determinants of quality of biological samples dedicated to FC analyses, it remains to be addressed by the investigators which is the fixative of choice for their specific research aims.

Investigating the Impact of Delivery System Design on the Efficacy of Self-Amplifying RNA Vaccines

messenger RNA (mRNA)-based vaccines combine the positive attributes of both live-attenuated and subunit vaccines. In order for these to be applied for clinical use, they require to be formulated with delivery systems. However, there are limited in vivo studies which compare different delivery platforms. Therefore, we have compared four different cationic platforms: (1) liposomes, (2) solid lipid nanoparticles (SLNs), (3) polymeric nanoparticles (NPs) and (4) emulsions, to deliver a self-amplifying mRNA (SAM) vaccine. All formulations contained either the non-ionizable cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or dimethyldioctadecylammonium bromide (DDA) and they were characterized in terms of physico-chemical attributes, in vitro transfection efficiency and in vivo vaccine potency. Our results showed that SAM encapsulating DOTAP polymeric nanoparticles, DOTAP liposomes and DDA liposomes induced the highest antigen expression in vitro and, from these, DOTAP polymeric nanoparticles were the most potent in triggering humoral and cellular immunity among candidates in vivo.

Immunophenotypic Characterization and Purification of Neoplastic Cells from Lymph Nodes Involved by T-Cell/Histiocyte-rich Large B-cell Lymphoma by Flow Cytometry and Flow Cytometric Cell Sorting

BACKGROUND

T-cell/histiocyte rich large B-cell lymphoma (THRLBCL) is B-cell lymphoma in which rare neoplastic cells are embedded in a reactive infiltrate. We describe the first characterization of the neoplastic cells by flow cytometry (FC).

METHODS

Using FC, we immunophenotyped the neoplastic cells of 11 cases of THRLBCL and 11 cases of DLBCL, NOS (controls). Neoplastic THRLBCL cells were also purified by flow cytometric cell sorting (FCCS).

RESULTS

A neoplastic THRLBCL population was detected by FC in 9 of 11 cases (82%). Neoplastic THRLBCL cells demonstrated an aberrant germinal center B-cell immunophenotype (bright CD20, bright CD40; positive for Bcl-6 and CD75; weakly positive for CD32; negative for IgH). With regard to adhesion molecules, CD54 was overexpressed, CD58 expression varied between cases, and CD50 expression was intermediate. Evaluation of immunomodulatory receptors demonstrated that PD-L2 was weakly expressed and PD-L1 was variably expressed. Finally, FCCS of two cases showed large multi-lobated cells with morphology consistent with neoplastic cells of THRLBCL.

CONCLUSIONS

The immunophenotype identified and the morphology of the FCCS purified cells confirms the FC defined populations are neoplastic cells from THRLBCL. While the cohort is small, neoplastic THRLBCL cells lack surface immunoglobulins. CD40, CD50, and CD54 were overexpressed in THRLBCL relative to DLBCL, NOS, perhaps contributing to the predominance of T cells in THRLBCL. Expression of CD32, PD-L1, and PD-L2 may be useful in distinguishing THRLBCL and NLPHL. Finally, the FC assays will be useful for purifying neoplastic cells of THRLBCL and for diagnostic immunophenotyping of THRLBCL. © 2019 International Clinical Cytometry Society.

Live Bacterial Vectors-A Promising DNA Vaccine Delivery System

Vaccination is one of the most successful immunology applications that has considerably improved human health. The DNA vaccine is a new vaccine being developed since the early 1990s. Although the DNA vaccine is promising, no human DNA vaccine has been approved to date. The main problem facing DNA vaccine efficacy is the lack of a DNA vaccine delivery system. Several studies explored this limitation. One of the best DNA vaccine delivery systems uses a live bacterial vector as the carrier. The live bacterial vector induces a robust immune response due to its natural characteristics that are recognized by the immune system. Moreover, the route of administration used by the live bacterial vector is through the mucosal route that beneficially induces both mucosal and systemic immune responses. The mucosal route is not invasive, making the vaccine easy to administer, increasing the patient's acceptance. Lactic acid bacterium is one of the most promising bacteria used as a live bacterial vector. However, some other attenuated pathogenic bacteria, such as Salmonella spp. and Shigella spp., have been used as DNA vaccine carriers. Numerous studies showed that live bacterial vectors are a promising candidate to deliver DNA vaccines.

A RHAG point mutation selectively disrupts Rh antigen expression

OBJECTIVES

The aim of this study was to characterise a novel mutation in the gene encoding RhAG in order to elucidate a molecular mechanism for Rh antigen expression and spherocytosis.

BACKGROUND

Rhesus-associated glycoprotein (RhAG) is critical for maintaining the structure and stability of erythrocytes. Single missense mutations in the gene encoding RhAG are sufficient to induce spherocytosis and deficiencies in Rh complex formation. We report a novel missense mutation that incompletely disrupts Rh antigen expression and selectively knocks out RhD antigen expression.

METHODS

Blood samples were taken from a 38-year-old male, his brother, his wife and his daughter in Xi'an, China. To detect the proband's RhAG and D antigen expression, the RBC were stained with anti-D and anti-RhAG and analysed by flow cytometry. Red blood cell morphology was detected with atomic force microscopy (AFM). Genomic DNA was isolated from whole blood samples, and the RHD, RHCE and RHAG alleles were sequenced and analysed. The mutation was mapped onto a predicted crystal structure of RhAG by the I-TASSER server and visualised using PyMOL.

RESULTS

Morphological testing by AFM found clear evidence of spherocytosis in the proband's erythrocytes. RHAG gene sequencing identified the mutation at sequence 236G > A, resulting in a serine to asparagine substitution at residue 79 (S79N). Family survey indicated that inheriting this allele is necessary and sufficient to cause the condition. Mapping the mutation onto a predicted crystal structure of RhAG revealed the proximity of the mutation to the critical structural elements of the protein.

CONCLUSIONS

A novel RHAG mutation significantly lowers RhAG antigen expression and antigen-mediated agglutination intensity.

Improved decision making for prioritizing tumor targeting antibodies in human xenografts: Utility of fluorescence imaging to verify tumor target expression, antibody binding and optimization of dosage and application schedule

Preclinical efficacy studies of antibodies targeting a tumor-associated antigen are only justified when the expression of the relevant antigen has been demonstrated. Conventionally, antigen expression level is examined by immunohistochemistry of formalin-fixed paraffin-embedded tumor tissue section. This method represents the diagnostic "gold standard" for tumor target evaluation, but is affected by a number of factors, such as epitope masking and insufficient antigen retrieval. As a consequence, variances and discrepancies in histological staining results can occur, which may influence decision-making and therapeutic outcome. To overcome these problems, we have used different fluorescence-labeled therapeutic antibodies targeting human epidermal growth factor receptor (HER) family members and insulin-like growth factor-1 receptor (IGF1R) in combination with fluorescence imaging modalities to determine tumor antigen expression, drug-target interaction, and biodistribution and tumor saturation kinetics in non-small cell lung cancer xenografts. For this, whole-body fluorescence intensities of labeled antibodies, applied as a single compound or antibody mixture, were measured in Calu-1 and Calu-3 tumor-bearing mice, then ex vivo multispectral tumor tissue analysis at microscopic resolution was performed. With the aid of this simple and fast imaging method, we were able to analyze the tumor cell receptor status of HER1-3 and IGF1R, monitor the antibody-target interaction and evaluate the receptor binding sites of anti-HER2-targeting antibodies. Based on this, the most suitable tumor model, best therapeutic antibody, and optimal treatment dosage and application schedule was selected. Predictions drawn from obtained imaging data were in excellent concordance with outcome of conducted preclinical efficacy studies. Our results clearly demonstrate the great potential of combined in vivo and ex vivo fluorescence imaging for the preclinical development and characterization of monoclonal antibodies.

Identification of Protective Antigens for Vaccination against Systemic Salmonellosis

There is an urgent medical need for improved vaccines with broad serovar coverage and high efficacy against systemic salmonellosis. Subunit vaccines offer excellent safety profiles but require identification of protective antigens, which remains a challenging task. Here, I review crucial properties of Salmonella antigens that might help to narrow down the number of potential candidates from more than 4000 proteins encoded in Salmonella genomes, to a more manageable number of 50–200 most promising antigens. I also discuss complementary approaches for antigen identification and potential limitations of current pre-clinical vaccine testing.

Pathogenic bacteria as vaccine vectors: teaching old bugs new tricks

As our scientific knowledge of bacteria grows, so does our ability to manipulate these bacteria to protect rather than infect mammalian hosts from a diverse group of diseases. The old axiom that the best way to protect from a disease is to get infected in the first place is not feasible in the face of the diverse group of pathogens that infect humans. Therefore, reprogramming bacteria to protect against diverse bacterial, viral, and parasitic diseases as well as cancer is a new reality in the field of vaccines.

Differential growth inhibition and enhancement of major histocompatibility complex class I antigen expression by interferons in a small-cell lung cancer cell line and its doxorubicin-selected multidrug-resistant variant

Expression of class I and class II major histocompatibility complex antigens on a human small-cell lung cancer cell line and its multidrug-resistant variant was examined before and after exposure to interferon alpha (IFN alpha) and IFN gamma by flow cytometry. Neither IFN alpha nor IFN gamma induced class II antigen expression on the drug-sensitive or resistant cell line. Induction of class I antigen expression along with an inhibition of proliferation was observed in both cell lines after IFN alpha treatment. On the other hand, IFN gamma treatment resulted in growth inhibition and enhancement of class I antigen expression in the sensitive cell line but not the resistant cell line. The differential response of the two cell lines to IFN gamma cannot be directly attributed to the acquisition of drug resistance but it suggests that further investigation of the possibility that drug-sensitive and resistant small-cell lung tumors may respond differently to immunotherapies that include IFN gamma is warranted.

Major histocompatibility complex class II antigen expression during potentiation of line-10 tumor immunity after intralesional administration of bacillus Calmette-Guérin

Intralesional injection of BCG into an established line-10 hepatocellular carcinoma in the strain-2 guinea pig causes regression of the tumor and induction of line-10 immunity. We found that the animals were already protected for a second challenge with line-10 tumor cells 7 days after BCG treatment. We studied whether this early induction of immunity was correlated with the expression of MHC class II antigens on line-10 tumor cells and was correlated with an increased expression of MHC class II antigens on leukocytes in the primary tumor and in the regional lymph node (Ln. axillaris accessorius). The MHC class II antigens and the leukocyte subpopulations were measured with monoclonal antibodies and flow cytofluorometry. In the draining lymph node the number of nucleated cells increased about 10-fold during the first 5 days after intralesional injection of BCG. At this time the MHC class II antigen expression of these cells was increased from 21%-32% in the naive controls to 39%-53% in animals with BCG-treated tumors. This implies that the number of MHC-class-II-positive cells increased about 20-fold in the draining lymph node. Surprisingly, the increase in percentage of MHC-class-II-antigen-positive cells was mainly due to an increase of IgM-positive B cells from 8%-11% to 22%-41% and an increase of IgG-positive B cells from 7%-27% to 25%-44%. In the tumor, BCG treatment induced a small increase of MHC-class-II-antigen-positive cells from 11%-12% to 15%-20%. Probably this increase came not from tumor cells but mainly from a BCG-induced infiltration of mononuclear cells, as an increase of T cells from 14% to 20%, an increase of macrophages from 8% to 18%, and an increase of B cells from 0 to 6% was observed. We conclude that the potentiation of anti-(line-10 tumor cell) immunity correlated with a 20-fold increase of MHC-class-II-antigen-positive cells in the lymph nodes and a small increase in the number of MHC-class-II-antigen-positive tumor-infiltrating cells.

Failure of specific adoptive immunotherapy owing to survival and outgrowth of variant cells

Adoptive immunotherapy, the transfer of spleen cells from immunized mice to mice with a small tumor, was usually curative for mice with the P815 mastocytoma provided that steps were taken to prevent the generation of tumor-induced suppressor cells in the recipient animal. However, failure of adoptive immunotherapy of the P815 tumor, resulting in regrowth of either the primary intradermal or a metastatic tumor, was observed in 10 out of 112 animals receiving graded doses of 7.5 x 10(7) to 3.0 x 10(8) immune spleen cells. Examination of the ten tumors in mice that failed to respond to therapy revealed that seven of them were significantly less susceptible than the original P815 tumor to rejection in vivo by transferred anti-P815-specific effector cells. In addition, nine of the ten therapy-failure tumors were also less susceptible than the original P815 tumor to lysis in vitro by P815-specific, but not DBA/2-specific, cytotoxic T lymphocytes. Sensitivity to lysis by tumor-specific cytotoxic T cells was not, however, strongly correlated with sensitivity to rejection in vivo by P815-specific effector spleen cells. Neither in vivo sensitivity to rejection, nor sensitivity to cytotoxic T cells, was correlated with alterations in class I major histocompatibility complex antigen expression. These results suggest that the survival and outgrowth of variant tumor cells was frequently the cause of failure of specific adoptive immunotherapy of the P815 tumor, and that selection for cells with a reduced sensitivity to killing by cytotoxic T cells was only one mechanism that might lead to an immunotherapeutic failure.

Modulation by cytokines of HLA antigens, intercellular adhesion molecule 1 and high molecular weight melanoma associated antigen expression and of immune lysis of clones derived from the melanoma cell line MeM 50-10

Clones were isolated from the cultured human melanoma cell line MeM 50-10, which metastasizes in nude mice with a pattern similar to that in patients with melanoma. Analysis with monoclonal antibodies detected heterogeneity among the clones in the expression of HLA class I antigens, HLA class II antigens, intercellular adhesion molecule 1 and high molecular weight melanoma associated antigen. The clones MeM A16 and MeM A18 were also shown to display differential susceptibility to modulation by immune interferon (IFN-gamma) and/or tumor necrosis factor (TNF-alpha) of the expression of the four types of antigens analyzed. In spite of differences in the antigenic profile, the two clones did not differ in their susceptibility to lysis by lymphokine-activated killer (LAK) cells and by anti-HLA-A2 cytotoxic T cells. The increase in the expression of HLA class I antigens induced by IFN-gamma and/or TNF-alpha on the two clones was associated with an increased susceptibility to lysis by anti-HLA-A2 cytotoxic T cells. Because of the metastasizing properties of cultured melanoma cells MeM 50-10, the clones we have isolated, with their distinct antigenic profile and differential susceptibility to modulation by cytokines, may represent useful models to investigate the role of distinct antigenic structures in the metastatic process.

DR antigen expression on ovarian carcinoma cells does not correlate with their capacity to elicit an autologous proliferative response

Expression of HLA-DR antigens by purified preparations of human ovarian carcinoma cells freshly isolated from surgical specimens was examined in parallel with the capacity of tumor cells to elicit a blastogenic response from autologous lymphocytes in mixed lymphocyte-tumor culture (MLTC) assay. Of 21 tumor preparations, 11 (52%) reacted with monoclonal antibodies 279 and/or 949 specific for a monomorphic determinant of HLA-DR antigens, with heterogeneous positivity, ranging between 30% and 95%. In this series of patients positive MLTC occurred in 8/21 individual experiments. The HLA-DR expression was proportionally similar in tumors giving positive MLTC (4/8 = 50%) and negative MLTC (7/13 = 53%). The lack of correlation between DR expression on tumor cells and stimulatory activity in autologous MLTC and the fact that DR-negative tumors could induce lymphocyte stimulation, support the hypothesis that blastogenesis occurs upon recognition of tumor-associated antigens, different from DR molecules, possibly tumor-specific antigens.

The immunological mouse mutants nude (nu) and rhino (hrrh) generate cytotoxic effector cells following adoptive immunotherapy but fail to reject a transplanted tumor

Adoptive immunotherapy, consisting of cyclophosphamide injection and the i.v. transfer of tumor-sensitized T cells, resulted in rejection of the immunogenic fibrosarcoma, MCA/76-9, by syngeneic C57BL/6J (B6) mice. The same treatment of tumor-bearing congenic immunodeficient mice, homozygous for the deleterious mutations nude (nu) and rhino (hrrh), did not result in tumor rejection. Paradoxically, the intratumor and intrasplenic changes taking place in each of the three strains after therapy were indistinguishable. There was an increase in Thy-1+, Ly-2+, or L3T4+ cells at the tumor site 8 days after adoptive immunotherapy and a similar increase in Thy-1+ cells in the spleen. Moreover, the T cells isolated from the tumors or spleens from each genotype were shown to be specifically cytotoxic in vitro as well as in an in vivo Winn assay. Further evidence that immune amplification had occurred in the immunological mutant mice was provided by experiments showing (a) the ability of spleen cells from tumor-bearers and those tested after therapy to produce IL-2 in response to Con A stimulation and (b) an increase in class II-MHC antigen expression by tumor-associated macrophages. The data suggest that, although amplification of antitumor immune responses occurred in the immunological mutants, the absence of a critical host factor limited the potency of the antitumor response.

Heterogeneous expression of a murine B16 melanoma-associated antigen correlates with cell cycle

A murine monoclonal antibody (MM2-3C6) that reacts with a B16 murine melanoma-associated membrane antigen was used to study the relationship of antigen expression to the cell cycle. Dual-parameter flow cytometric measurements of membrane antigen and DNA revealed that antigen-positive cells were present throughout the cell cycle. Peak antigenic expression was noted during the late log phase of the cell growth curve with negligible antigen-negative population. The emergence of a distinct antigen-negative population (30%-40%) was noted in the late stationary phase. Cell cycle analysis indicated that the negative subpopulation was restricted to the G0/G1 phase, thus, demonstrating antigenic heterogeneity within the tumor cell population. Cell sorting was performed to analyze the origin of such heterogeneity. Following two sequential sortings, the antigen-negative cells became antigenic upon reculture. Again, at the late stationary phase, a distinct antigen-negative population (30%-40%) emerged. The sorted antigen-positive cells showed flow cytometric profiles identical to the sorted antigen-negative population upon reculture. Therefore, in this murine model, it appears that antigen expression is cell cycle dependent and such expression seems to be associated with proliferation.

High concordance between marker profiles of 22 human leukemia-lymphoma cell lines tested with the same monoclonal antibodies before and during the second international workshop on human differentiation antigens

Our laboratory participated in the Second International Workshop and Conference on Human Leucocyte Differentiation Antigens. In this international study the reactivity profiles of monoclonal antibodies were analyzed on normal and malignant hematopoietic cells. The Workshop was divided into three categories: the T-cell, B-cell and myelomonocytic cell studies. We blindly tested 159 coded monoclonal antibodies of the panel for the T-cell study on 22 permanently established leukemia cell lines. The monoclonal antibodies were provided by the Workshop Committee and their reactivity with the target cells was visualized by standardized indirect immunofluorescence. After decoding it was recognized that 11 monoclonal antibodies had been examined on these cell lines prior to the Workshop. The reactivity of these 11 monoclonal antibodies was analyzed and compared with the earlier results. From a total of 217 paired tests done blindly in the Workshop study and prior to the Workshop, 191 tests (88%) did not show significantly different data. The possible reasons for discrepancies include nonspecific Fc-receptor-binding on some cell lines and a relatively nonspecific reactivity of some monoclonal antibodies. This analysis demonstrates the stability of the antigen expression on human leukemia-lymphoma cell lines grown at consistently optimal conditions, for the tests, using the same monoclonal antibodies as in the Workshop, had been performed 0.5-5 years prior to the Workshop study. On the other hand, nonspecific Fc-binding, wide "specificity" of monoclonal antibodies and a shift in antigen expression of the cells (due to poor growth conditions, involuntary induction of differentiation and other factors) must be taken into consideration upon immunological analysis.

T cell surface antigen expression on lymphocytes of patients with AIDS during in vitro mitogen stimulation

Surface marker expression on peripheral blood mononuclear cells (PBMC) was evaluated daily in PHA- and PWM-stimulated cultures of eight AIDS patients and eight normals. Before culture, the patients' cells showed the characteristic decrease in OKT 4+ cells (normals 40.4%, patients 22.3%; P less than 0.001), increase in OKT 8+ cells (normals 27.6%, AIDS 38.4%; P = 0.002), increase in OKT 10+ cells (normals 15.5%, AIDS 42.8%; P = 0.002), and increase in HLA-DR+ cells (normals 11.4%, AIDS 28.7%; P = 0.01). The percentage of OKT 11+ cells remained unchanged, while the percentage of OKT 3+ cells dropped over the first 2 days in PHA but not in PWM cultures of both groups (PHA: normals 69.8% to 35.1%; P = 0.001, AIDS 56.5 to 38.5%; P = 0.001, PWM: normals 62.8%-65.9%, AIDS 66.8% to 63.9%), and recovered in both groups by day 5. In PWM cultures OKT 3+ cells increased significantly in normals but not in AIDS (normals 62.6%-77.7%; P = 0.04, AIDS 61.8 to 48.7%). OKT 4 expression decreased in normal PHA cultures after 1 day (38.9% to 29.6%; P = 0.05) and then recovered by day 5. Its expression increased in AIDS PHA cultures by day 5 (18.0%-41.1%; P less than 0.001). The final percentage of OKT 4+ cells in AIDS cultures was within the normal range (35.0%-49.0%). OKT 8 expression increased in both study groups after PHA stimulation (normals 29.5%-50.4%; P = 0.002, AIDS 37.4%-50.7%; P = 0.02) and in normals but not AIDS after PWM stimulation (normals 28.9%-35.5%; P = 0.004, AIDS 38.5%-35.6%). Because of the relative changes in expression of OKT 4 and OKT 8, the 4/8 ratio declined in the normal PHA cultures (1.89 to 1.03; P = 0.1) and increased in the AIDS cultures (0.68-1.18; P = 0.09). Also, the sum of OKT 4+ and OKT 8+ cells in PHA cultures increased from 68% to 94% whilst expression of OKT 11 remained unchanged, indicating co-expression of these antigens on individual cells. Both PHA-and PWM-stimulated normal cells showed an increase in OKT 10 (PHA 16.0%-53.4%; P = 0.01, PWM 16.1%-33.9%; P = 0.03) and HLA-DR (PHA 8.6%-27.3%; P = 0.03, PWM 12.5%-26.6%; P = 0.07). In AIDS PHA cultures this did not change, and in their PWM cultures OKT 10 expression declined (44.8 to 23.0%; P = 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Functional consequence of variation in melanoma antigen expression

Melanoma cells have been shown to express melanoma-associated antigens and, in many cases, the histocompatibility antigen, HLA-DR. We questioned whether the expression of these antigens was quantitatively altered during the serial passage of melanoma cells in culture. Therefore, we measured the binding of monoclonal antibodies specific for a melanoma-specific antigen and the HLA-DR antigen to melanoma cells from serial passages. Three cell lines were studied. We found that although both the melanoma-associated antigen and the HLA-DR antigen were qualitatively conserved, significant quantitative differences were seen. To study the functional consequences of these differences, we used fluorescence-activated cell sorting to create DR-enriched and DR-depleted populations from a single melanoma cell line heterogeneous for DR expression. We found that the proliferation of allogeneic T cells (measured by the 3H-TdR uptake) cultured with the DR-enriched and -depleted melanoma cell populations was directly related to the amount of the HLA-DR antigen expressed. These results indicate that in performance of experiments using melanoma cell lines quantitative assessment of antigenic expression is important, particularly if the function of a specific antigen is under examination. Further, our data clearly identify the HLA-DR antigen on melanoma cells as a participant in allogeneic lymphocyte stimulation.

Clonal analysis of expression of tumor-associated transplantation antigens and of metastatic capacity

ESb, a spontaneous high metastatic variant of the chemically induced T lymphoma Eb, was found previously to express a tumor-associated transplantation antigen (TATA) that was different from that of the parental line. Syngeneic tumor-specific cytolytic T lymphocytes (CTL) were able to recognize the different TATAs of Eb and ESb in vitro and could therefore be used for routine typing. The object of this study was to investigate tumor antigen expression on a clonal level and to compare the in vitro data with the in vivo behavior of the same cell lines.

Our CTL typing analysis of cloned tumor lines revealed that the two populations, Eb and ESb, are distinct and relatively homogeneous with regard to their TATA expression. Furthermore, all ESb clones formed rosettes with antibody-coated erythrocytes, while none of the parental type Eb clones showed this characteristic. The sensitivity to tumor-specific CTL lysis varied with time of tumor cell culture in vitro in a clone-dependent manner.

Variability was also noted in vivo in tumor growth and metastatic spread. Of over 50 ESb clones tested, the majority were highly metastatic while a minority were significantly lower in metastatic capacity. High and low metastatic ESb clones could not be distinguished by their expression of TATAs and of Fc receptors. There was also a considerable individual variability in the hosts, although they were genetically identical. This variability was most probably due to differences in the immune status of the animals.