Cytokeratin immunoreactivity in lobular intraepithelial neoplasia.

Eighteen commercially available antibodies reactive against different cytokeratin proteins were tested on classic examples of lobular intraepithelial neoplasia (LIN) and of ductal intraepithelial neoplasia (DIN) of the breast. About 90% of higher-grade DIN (AIDH and DCIS) show no or substantially diminished reaction with clone 34betaE12 (specified as reactive against keratins 1, 5, 10, and 14 as determined by the manufacturer), while the cells of LIN were found to express the antigen reactive with this antibody. To determine which of these four keratins are present in the cells of LIN, antibodies reactive against these individual four keratins were tested. None of the four antibodies to keratins 1, 5, 10, or 14 reacted with the cells of LIN. To investigate this further, 13 additional monoclonal antibodies to various other keratin proteins were tested on the cells of LIN. Those that successfully reacted with the cells of LIN were further tested on the cells of DIN. All of the individual antibodies reactive with the cells of LIN were also reactive with the cells of DIN to a degree, with clone RCK108 (reactive against keratin 19) coming the closest to demonstrating the reactivity seen with 34betaE12. We conclude that the reactivity seen in the cells of LIN with 34betaE12 is due to either (a) a crossreaction with keratin 19 that is slightly less prominent than the reaction of the individual clone RCK108, (b) a crossreaction with a keratin protein that was not tested (3, 11, 12), (c) a crossreaction with a protein closely resembling keratin in formalin-fixed, paraffin-embedded tissue, or (d) the detection of a mutated or truncated form of keratin 1, 5, 10, or 14 that cannot be detected by the individual monoclonal antibody.     

Trypanosoma lewisi: stage-specific surface antigens and exoantigens recognized by monoclonal antibodies

The stage-specific expression of surface antigens by Trypanosoma lewisi was investigated using monoclonal antibodies directed against this parasite. Hybridomas secreting monoclonal antibodies were produced by the fusion of SP2/0-Ag 14 mouse plasmacytomas with spleen cells from rats infected previously with the Taliaferro strain of T. lewisi. Additivity enzyme-linked immunosorbent assays and indirect immunofluorescent antibody tests indicated the determinant recognized by monoclonal antibody TL40.3 (IgM) was different from those recognized by monoclonal antibodies TL40.1 (IgA), TL40.2 (IgM), and TL40.6 (IgG2 alpha). Monoclonal antibody TL40.3 agglutinated trypanosomes collected 3 days after parasite inoculation while monoclonal antibodies TL40.1, TL40.2, and TL40.6 agglutinated trypanosomes collected 6 days after inoculation. Since agglutinin titers against trypanosomes from irradiated (700 rad from a 60Co source) and nonirradiated rats were similar, expression of the antigens recognized by the monoclonal antibodies appeared to be independent of the immunological state of the host and the morphology of the parasite. The reproduction of T. lewisi in in vitro trypanostatic assays was inhibited only when the monoclonal antibodies were present in concentrations greater than or equal to those needed to agglutinate the trypanosomes. Monoclonal antibodies TL40.1 and TL40.3, but not TL40.2 and TL40.6, agglutinated erythrocytes collected later in the infection from irradiated, infected rats. None of the monoclonal antibodies agglutinated erythrocytes from nonirradiated, infected rats, from irradiated, noninfected rats or from nonirradiated, noninfected rats. This suggests that immunocompetent rats may make blocking antibodies against the exoantigens recognized by monoclonal antibodies TL40.1 and TL40.3.     

An immunocytochemical study of keratin reactivity during rat odontogenesis

Summary The cytokeratin distribution in the developing rat enamel organ from day 15 of gestation through to 11 days post partum was examined immunohistochemically using a panel of monoclonal antibodies. A temporo-spatial programme of keratin expression was observed during odontogenesis and positive reactivity of the enamel organ was seen with the pan keratin antibodies CK1 (clone LP34 — reacts with a number of keratins including 6 and 18) and AE1-3 (reacts with most acidic and basic keratins). No reactivity was observed in the enamel organ with the other antibodies examined (Ks 8.12 [reacts with keratins 13 and 16], Ks 8.60 [reacts with keratins 10 and 11) and MCA157 [reacts with rat liver antigen]), although these antibodies did stain other epithelial tissues. This study supports the view that the epithelial cells of the enamel organ synthesize a tissuspecific subset of keratins which are related to the differentiation of the cells.     

Comparison of cellular phenotypes in tumor cyst and ascitic fluid from ovarian serous carcinoma.

Density gradient centrifugation was applied to isolate cell subsets from tumor cyst and ascitic fluid in eight patients with ovarian serous carcinoma. A comparison of cellular composition and immunologic reactivity of cells from the cysts and from ascitic fluid in each patient was performed. Some differences in density profiles were found, but in each case the consistency of morphologic cell forms in the primary tumor and ascites was documented. Immunophenotypic analyses of isolated cellular fractions using polyclonal and monoclonal antibodies against ovarian carcinoma-associated antigens showed significant immunologic intratumoral heterogeneity. However, there was a similarity of antigen expression in cells from the primary tumors and ascitic fluids. Our study indicated that morphologic and antigenic characterization of a given tumor could be determined in a single representative sample of ascitic fluid.     

Immunolocalization of keratin polypeptides in human epidermis using monoclonal antibodies

Three monoclonal antibodies (AE1, AE2, and AE3) were prepared against human epidermal keratins and used to study keratin expression during normal epidermal differentiation. Immunofluorescence staining data suggested that the antibodies were specific for keratin-type intermediate filaments. The reactivity of these antibodies to individual human epidermal keratin polypeptides (65-67, 58, 56, and 50 kdaltons) was determined by the immunoblot technique. AE1 reacted with 56 and 50 kdalton keratins, AE2 with 65-67 and 56-kdalton keratins, and AE3 with 65-67 and 58 kdalton keratins. Thus all major epidermal keratins were recognized by at least one of the monoclonal antibodies. Moreover, common antigenic determinants were present in subsets of epidermal keratins. To correlate the expression of specific keratins with different stages of in vivo epidermal differentiation, the antibodies were used for immunohistochemical staining of frozen skin sections. AE1 reacted with epidermal basal cells, AE2 with cells above the basal layer, and AE3 with the entire epidermis. The observation that AE1 and AE2 antibodies (which recognized a common 56 kdalton keratin) stained mutually exclusive parts of the epidermis suggested that certain keratin antigens must be masked in situ. This was shown to be the case by direct analysis of keratins extracted from serial, horizontal skin sections using the immunoblot technique. The results from these immunohistochemical and biochemical approaches suggested that: (a) the 65- to 67-kdalton keratins were present only in cells above the basal layer, (b) the 58-kdalton keratin was detected throughout the entire epidermis including the basal layer, (c) the 56- kdalton keratin was absent in the basal layer and first appeared probably in the upper spinous layer, and (d) the 50-kdalton keratin was the only other major keratin detected in the basal layer and was normally eliminated during s. corneum formation. The 56 and 65-67- kdalton keratins, which are characteristic of epidermal cells undergoing terminal differentiation, may be regarded as molecular markers for keratinization.     

An immunocytochemical study of keratin reactivity during rat odontogenesis.

The cytokeratin distribution in the developing rat enamel organ from day 15 of gestation through to 11 days post partum was examined immunohistochemically using a panel of monoclonal antibodies. A temporo-spatial programme of keratin expression was observed during odontogenesis and positive reactivity of the enamel organ was seen with the pan keratin antibodies CK1 (clone LP34 - reacts with a number of keratins including 6 and 18) and AE1-3 (reacts with most acidic and basic keratins). No reactivity was observed in the enamel organ with the other antibodies examined (Ks 8.12 [reacts with keratins 13 and 16], Ks 8.60 [reacts with keratins 10 and 11) and MCA157 [reacts with rat liver antigen]), although these antibodies did stain other epithelial tissues. This study supports the view that the epithelial cells of the enamel organ synthesize a tissue-specific subset of keratins which are related to the differentiation of the cells.     

Density distribution, cytomorphologic features and immunologic characteristics of ovarian and endometrial clear cell carcinomas

Three subpopulations of cancer cells with different morphologic features were separated by density gradient centrifugation of two ascitic fluids and one cystic fluid from one patient with ovarian clear cell carcinoma and one with endometrial clear cell carcinoma. Immunophenotypic analyses of isolated fractions using polyclonal and monoclonal antibodies against ovarian carcinoma-associated antigens revealed significant immunologic heterogeneity among the tumor cells. The identical histopathologic structures of the ovarian and endometrial clear cell carcinomas and the similar distribution and immunologic reactivity of the cell types isolated from the ascitic and cystic fluids confirmed the common histogenesis of both cancers. These findings suggest that the conventional cytologic diagnosis of clear cell carcinomas could be supplemented by immunofluorescent staining. Density gradient centrifugation appeared to be a useful method for the separation of mesothelial cells.     

Correlation of specific keratins with different types of epithelial differentiation: monoclonal antibody studies

We have prepared three monoclonal antibodies against human epidermal keratins. These antibodies were highly specific for keratins and, in combination, recognized all major epidermal keratins of several mammalian species. We have used these antibodies to study the tissue distribution of epidermis-related keratins. In various mammalian epithelia, the antibodies recognized seven classes of keratins defined by their immunological reactivity and size. The 40, 46 and 52 kilodalton (kd) keratin classes were present in almost all epithelia; the 50 kd and 58 kd keratin classes were detected in all stratified squamous epithelia, but not in any simple epithelia; and the 56 kd and 65-67 kd keratin classes were unique to keratinized epidermis. Thus the expression of specific keratin classes appeared to correlate with different types of epithelial differentiation (simple versus stratified; keratinized versus nonkeratinized).     

Human eccrine sweat gland. Expression of neuroglandular antigens and coexpression of intermediate filaments.

Acrosyringium, duct and secretory epithelium as well as myoepithelial cells of human eccrine sweat glands have been characterized by different immunostaining patterns with mono- and polyclonal antibodies to a wide spectrum of tissue antigens. Using monoclonal antibodies to neuron-specific enolase (NSE) and melanoma-associated antigens (LS 59, HMB-45, NKI/C-3) the expression of neuroectodermal antigens in secretory coils was demonstrated. Myoepithelial cells were double-stained with polyclonal vimentin and monoclonal CAM 5.2 (against keratins nos. 8, 18, 19) antibodies.     

Cell surface antigens during submerged development of Myxococcus xanthus examined with monoclonal antibodies

Eighteen monoclonal antibodies directed against cell surface antigens of Myxococcus xanthus were followed by enzyme-linked immunosorbent assay. Three of the monoclonal antibodies were specifically directed against antigens present only on cells undergoing fruiting body development. These cell surface antigens became detectable by the early preaggregation stage (2 to 4 h) of development and increased until early aggregation (9 to 10 h), after which the concentrations of two of the cell surface antigens remained constant and the concentration of the third decreased. The remaining 15 monoclonal antibodies recognized cell surface antigens that were shared by vegetative and developing cells. Based on their relative concentrations during development, these shared antigens can be grouped into three classes. In the first class antigen concentration remained constant, in the second it decreased, and in the third it increased. Western blots of cell surface antigens were probed with monoclonal antibodies. Five monoclonal antibodies reacted with material in distinct bands, five monoclonal antibodies reacted with multiple, diffuse bands, and eight monoclonal antibodies were not reactive in Western blots.     

Major-histocompatibility-complex-class-II-positive cells and interleukin-2-dependent proliferation of immune T cells are required to reject carcinoma cells in the guinea pig

Summary Tumor immunity induced by bacillus Calmette-Guérin was studied in the line 10 hepatocellular carcinoma (line 10) in the strain-2 guinea pig. Line 10 immunity was investigatedin vitro with a lymphocyte proliferation assay using line 10 tumor protein extracted with 3 M KCl andin vivo by adoptive transfer of line-10-immune spleen cells. Monoclonal antibodies against guinea pig leucocyte markers were used to block functional properties of the immune cells in order to determine which cell types or cell markers are involved in the immune response to the line 10 tumor.In vitro cells from the spleen, peripheral blood and regional lymph node of immune animals reacted with a proliferative response to line 10 protein. This antigen-specific response was caused by T cells and was regulated by major histocompatibility complex (MHC) class II molecules. In blocking experiments it was found that CT5 (anti-PanT), or MSgp4 [anti-(MHC class I antigen)] monoclonal antibodies did not block but some-times stimulated the proliferative response. The effect of H159 (anti-PanT) was irregular, while H155 [anti-(T helper)], and 5C3 [anti-(IL-2 receptor)] monoclonal antibodies blocked the response almost completely. We studied the relevance of the resultsin vitro obtained and found that mAb 5C3 [anti-(IL-2 receptor)] inhibited the adoptive transfer of line 10 immunity, suggesting that the rejection of line 10 cells is caused by a mechanism that is interleukin-2 (IL-2)-dependent. Moreover, complement lysis of MHC-class-II-antigen-positive immune spleen cells inhibited completely the rejection of the line 10 tumor cell challenge in the adoptive-transfer experiments. In conclusion, our data show that MHC class II molecules or cells possessing these molecules are involved in immunity against line 10 tumor cells, as (a) monoclonal antibodies against MHC class II antigens inhibited thein vitro proliferative response of T cells to tumor antigens and (b) removal of MHC-class-II-positive immune spleen cells abrogated the antitumor effect in the adoptive-transfer experiments. Interleukin-2-dependent proliferation of immune T cells is required for the rejection of line 10 tumor cells.     

Immunogold labeling of keratin filaments in normal human epidermal cells with two anti-keratin monoclonal antibodies

We report on application of the highly sensitive and specific immunogold labeling method for ultrastructural investigation of keratin intermediate filament antigens in human epidermal cell suspensions. Triton X-100 pretreated cells proved accessible to the colloidal gold conjugate, thus enabling keratin filament bundles to be labeled. Anti-keratin KL1 and KL2 monoclonal antibodies were raised in mice after immunization with either human stratum corneum-isolated keratins or keratins extracted from human epidermal cells suspensions, respectively. Immunoelectron microscopy confirmed immunofluorescence and immunoperoxidase results of epidermal keratinocyte staining, and revealed two different antibody reactivity patterns: KL2 reacted with keratin filaments in keratinocytes of all epidermal layers, whereas antigen to KL1 was detected only on keratin of the suprabasal layers, not on the basal keratinocyte tonofilaments. The monoclonal antibody-recognized epitopes were specific for the keratin filaments. Vimentin-rich cells (melanocytes) were not stained in the same epidermal cell suspensions. Additionally, two distinct ultrastructural patterns of keratin filament epitope labeling were observed. KL1 and KL2 monoclonal antibodies react with two different antigenic determinants, depending on the stage of keratinocyte differentiation, and may therefore be used for immunohistochemical studies of various keratin-containing cells in normal and pathologic conditions.     

Murine leukemia cell hybrids: The quantity of TL antigens expressed by parental and hybrid cells fails to correlate with their sensitivity to TL antibody and complement

The quantity of thymus-leukemia (TL) antigens expressed by murine leukemia cells is significantly greater than that expressed by somatic hybrids of such cells. Based upon the results of ¹²⁵I-lactoperoxidase labeling and antibody absorption procedures, and corrected for size differences between the two cell types, the quantity of TL antigens expressed by RADA-1 cells, a radiation-induced murine leukemia cell line of strain A/J mice, is approximately 5.0 times greater than that of somatic hybrids of RADA-1 and LM(TK)^? cells. LM(TK)^? cells are a thymidine kinase-deficient TL(-) mouse fibroblast cell line. The quantity of TL antigens expressed is related only in part to their susceptibility to lysis by TL antibodies and guinea pig complement (GPC). RADA-1 cells resist lysis. The quantity of TL antigens expressed by RADA-1 cells is analogous to that formed by nonneoplastic thymocytes obtained from F₁ hybrids of two strains of TL(+) and TL(-) mice; cells from both strains are sensitive to TL antiserum and GPC. ASL-1 cells, a spontaneously occurring leukemia cell line of A/J mice, express TL antigens in significantly higher quantities than any of the cell types examined. Exposed to TL antisera, the quantity of TL antigens of ASL-1 cells, but not that of hybrid cells, gradually diminishes. ASL-1 cells convert over a 6-h period of exposure to antibody and guinea pig complement (GPC) resistance; hybrid cells remain sensitive. However, ASL-1 cells converted to TL antibody and GPC resistance continue for a time to express TL antigens in quantities similar to that of sensitive F₁ thymocytes and resistant RADA-1 cells. RADA-1 X LM(TK)^? hybrid cells, which are sensitive to TL antibodies and GPC, express the lowest quantities of TL antigens of any of the cell types examined. It is likely that differences in the quantities of TL antigens expressed by different cell lines reflect genetic mechanisms controlling TL antigen expression. The failure of TL antisera to affect the quantities of TL antigens expressed by hybrid cells is taken as an indication that genetic controls governing antigen expression may be distinguished from those involved in regulating responsiveness to specific antiserum.     

High frequency of natural autoantibodies in normal newborn mice

Spleen cells from 6-day-old nonimmunized BALB/c and BALB.B10 mice were fused with the nonsecreting hybridoma cell line Sp2/0. Three hundred and eighty-four immunoglobulin-secreting hybrids were screened for antibody activity against mouse actin, tubulin, and myosin, and against TNP, peroxidase, renin, DNA, and neurofilaments. At least 24 hybridomas in the collection (6.25%) exhibited antibody activity against this panel of antigens. Ten of these hybrids were cloned, were propagated, and the corresponding monoclonal IgM protein was isolated from ascitic fluids and was further characterized. At least four groups of antibody specificities were identified: 1) one clone reacting with TNP only; 2) one clone reacting with both actin and tubulin; 3) two clones which bound to both TNP and actin; and 4) a fourth group, comprising the six other clones, which all exhibited widespread reactivity and bound to actin, tubulin, myosin, and TNP. These results indicate: 1) B cell clones directed against self antigens are activated in the internal environment and are recovered consequently by somatic cell hybridization; 2) the widespread antibody specificities found for these newborn mouse antibodies are very similar to those previously characterized with human natural antibodies and human monoclonal Ig; and 3) the frequency of B cells binding to cytoskeletal proteins and TNP is very high (at least 6.25%).     

Isolation of twelve monoclonal antibodies against Ia and H-2 antigens. Serological characterization and reactivity with B and T lymphocytes

The cell hybridization technique was used for the production of 12 monoclonal antibodies against H-2K^k, H-2D^b, I-A^k and I-E^k antigens. The strain distribution pattern indicated that three antibodies reacted with new H-2 and Ia determinants, respectively, while the majority of determinants defined by the monoclonal antibodies showed good correlation with H-2 and Ia determinants described by conventional alloantisera.Monoclonal Ia antibodies showed strong reactivity with about 90% of surface IgM positive B cells, but not with T cells. In double fluorescence studies, both I-A and I-E determinants were always found to be coexpressed on the same B cells. When the high sensitivity of the fluorescence activated cell sorter was utilized, about 30 to 40% of purified lymph node T cells were found to carry both I-A and I-E antigens, although in a much lower density than B cells. In conclusion, monoclonal Ia antibodies appear to display the same serological and cellular reactivity pattern as do conventional antisera.     

Characteristics of monoclonal antibodies reactive with human sperm and seminal plasma

The characteristics of monoclonal antibodies developed against human spermatozoa are described. Out of 10 monoclonal antibodies 9 did not react in ELISA with human RBC, WBC, platelets, Raji cells nor mouse sperm. Four monoclonal antibodies reacted with monkey sperm and all 10 reacted with human seminal plasma. Monoclonal antibodies showed differential reactivity with pre- and post-capacitated sperm. Four monoclonal antibodies were able to agglutinate sperm whereas none of these were positive in sperm-immobilization assay. Interestingly, two monoclonal antibodies (MA-46 and MA-50) were able to block the attachment of pre-capacitated sperm to zona denuded hamster oocytes. MA-46 and MA-50 recognized in immunoblot spermatozoa antigens having apparent molecular weights of 14 and 20 K Da and greater than 200 K Da respectively. The monoclonal antibodies reported in this study will be useful in further delineating the spermatozoa antigens involved in regulation of fertility.     

The human thymic microenvironment: Thymic epithelium contains specific keratins associated with early and late stages of epidermal keratinocyte maturation

Normal T-cell development is dependent on interactions with the thymic microenvironment; thymic epithelial cells are thought to play a key role in the induction of thymocyte maturation, both through direct contact and, indirectly, via thymic hormone secretion. It has been postulated that thymic epithelial cells progress through an antigenically defined pathway of differentiation similar to that of epidermal keratinocytes. As keratins vary according to epithelial cell type and the stage of epithelial cell maturation, we used a panel of monoclonal antibodies against keratins to study specific types of keratin intermediate filaments within human thymic epithelium. The demonstration in human thymus of keratins previously shown to be associated with distinct stages of epidermal keratinocytic maturation would support the hypothesis that thymic epithelial cells undergo sequential stages of differentiation. Two-dimensional immunoblot analysis of cytoskeletal extracts from human thymus revealed that thymic epithelium contains the following keratins: 1-2, 5, 6, 7, 8, 10, 13, 14, 15, 16, and 17 (molecular masses, 65-67, 58, 56, 54, 52, 56.5, 51, 50, 50', 48, and 46 kilodaltons, respectively). Thus, in thymic epithelium, we found keratins previously observed in epidermal basal cells (5, 14, 15), as well as keratins specific for terminally differentiated keratinocytes in supra-basal epidermis (1-2, 10). Indirect immunofluorescence (IF) performed on fetal and postnatal human thymus demonstrated that keratin epitopes recognized by antibodies AE-3, 35 beta H11, and RTE-23 are present on epithelial cells of the subcapsular cortex, the cortex, the medulla, and Hassall's bodies. In contrast, antibodies AE-1 and RTE-22 reacted primarily with neuroendocrine thymic epithelium (subcapsular cortex, medulla, Hassall's bodies). The epithelial reactivity of antibody AE-2 was limited to epithelial cells in Hassall's bodies and did not appear until 16 weeks of fetal gestation i.e., when Hassall's bodies first formed. Two-dimensional gel analysis of thymic keratins demonstrated that antibody AE-2 identified only the keratins with molecular masses of 56.6 and 65-67 kilodaltons (10 and 1-2 respectively) in thymus. These data, together with the selective reactivity of AE-2 with Hassall's bodies in fluorescence assays, demonstrate the localization in Hassall's bodies of the high-molecular-weight keratins associated with the late stages of epidermal cell maturation. In summary, we demonstrated that human thymic epithelium contains specific keratins found in multiple epithelial types as well as keratins associated with both early and late stages of epidermal cell differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Production and Preliminary Application of Monoclonal Antibodies Against Paulownia Witches' Broom MLO

Monoclonal antibodies against mycoplasma-like organisms (MLO) associated with paulownia witches’broom (PWB) were produced by using partially purified preparations from diseased paulownia. Splenic cells from immunized mice were fused with sp2/0murine myeloma cells. Screened by indirect ELISA using partially purified PWB-MLO and healthy paulownia extracts as detecting antigens, two hybridoma clones that stably secreted specific antibodies against PWB-MLO were obtained from 459 clones of four successful fusions. The monoclonal antibodies were isotyped and determined to be immunoglubin classes IgG2a and IgG3. Antibody titers of ascitic fluids were both over 1.6 × 104 assayed by indirect ELISA. Priliminary application on several specimens proved that they were the monoclonal antibodies against PWB-MLO.     

Expression of markers shared between human natural killer cells and neuroblastoma lines

Summary Neuroblastoma is a tumor of neuroectodermal origin arising most commonly from the adrenal medulla. We have examined the ability of several monoclonal antibodies which recognize markers predominantly expressed on human natural killer (NK) cells to react with neuroblastoma cell lines in vivo derived sections of tumor. HNK-1 (Leu 7) is a monoclonal IgM antibody which recognizes a carbohydrate epitope on NK cells and a wide range of tumor cell types. We have shown that HNK-1 recognizes the human neuroblastoma lines SMS-KCNR, SMS-KAN, NMB/N7, and IMR/5. Expression of this antigen on cell lines can be slightly increased by retinoic acid-induced differentiation of the cells. N901 (NKH1), a monoclonal antibody raised against interleukin 2-dependent human NK cell lines also recognizes all human neuroblastoma cell lines examined. This expression is independent of differentiation induction and levels remain unaltered following retinoic acid treatment of the cell lines. Lastly, with monoclonal antibody 49H.8, it has been found that reactivity of the lines is weak until induction of differentiation, after which highly significant increases of reactivity are seen. 49H.8 recognizes several cryptic carbohydrate antigens with varying affinities, shown to identify mouse and rat NK cells. In contrast to other NK markers, human neuroblastoma cell lines did not express significant reactivity with B73.1, Leu 11b, or Leu 18. Immunohistochemical staining of sections of human neuroblastoma tumors correlated with the in vitro findings; however, staining with N901 and 49H.8 was only seen on frozen sections, not paraffin-embedded. The significance of shared NK cell-neuroblastoma/neuron antigens is currently under investigation.     

Sharing of Ia antigens between species. IV. Interspecies cross-reactivity of monoclonal antibodies directed against polymorphic mouse Ia determinants

The specificity of interspecies Ia cross-reactions has been analyzed by testing a panel of monoclonal antibodies (mAb) to mouse I-E and I-A antigens for reactivity with pig Ia antigens. Our earlier studies showed that mouse anti-I-E alloantisera recognized common determinants on Ia antigens of other species, whereas anti-I-A alloantisera showed much more limited cross-reactivity. These results were confirmed using a panel of 17 anti-I-E mAb, 10 of which were cytotoxic to pig cells. 2D gel electrophoretic analyses of precipitates with these mAb of 35S-labeled, NP40 solubilized pig cells revealed a limited set of protein spots that appeared to be identical to the subset of pig Ia antigens precipitated by A.TH anti-A.TL alloantiserum. Because the cross-reactive mouse sera were produced in mouse strains that do not express an I-E molecule (H-2b and H-2s), it was anticipated that the cross-reacting antibodies would be reactive with the monomorphic determinant of the I-E molecule, Ia.7. However, comparison of the reactivity of these mAb with pig cells and mouse cells revealed that the cross-reactivity on pig cells correlated not with Ia.7 but rather with detection of epitope(s) of the I-E molecule associated with inter-strain polymorphism. Anti-I-A cross-reactions were also detected, but were weaker and more limited. These findings may have implications for the evolution of Ia antigens in mammalian species.