Avidin-biotin Immunoperoxidase Staining Research Articles

Characterisation of cell types in abalone ( Haliotis spp.) tissues using immunohistochemical techniques

The increasing popularity of abalone as a seafood delicacy has led to the rapid development of abalone aquaculture worldwide. The commercial and economic importance of this industry has resulted in an increasing interest in the biology of this particular shellfish genus. In this study we focus on the identification of structural, functional and proliferative proteins in two species of abalone shellfish, Haliotis discus hannai and Haliotis tuberculata. Monoclonal and polyclonal antibodies that react with proteins in vertebrate and invertebrate tissues were selected and applied to abalone tissues. Cross sections of whole animals were analysed using avidin–biotin immunoperoxidase staining protocols. In total, twenty-four antibodies were tested on shellfish tissues. Six antibodies out of twenty-four detected antigens in Haliotis spp. Cytokeratins, proliferating cell nuclear antigen (PCNA), neuron specific enolase (NSE), laminin and vimentin were detected in abalone tissues. Positive immunohistochemical results were confirmed using western blot. The expression of these proteins aids in the characterisation of cell types present in abalone tissues, which contributes to a better understanding of the fundamental biology of this shellfish genus.

Atopic dermatitis: immunophenotyping of inflammatory cells in skin lesions.

The ever increasing incidence of atopic dermatitis (AD) has stimulated many researchers to use various diagnostic procedures to obtain new data to help elucidate the pathogenesis of the disease. To perform cell immunophenotyping and to analyze the presence of inflammatory cell-surface markers in the biopsies of skin lesions from 15 AD patients and five healthy subjects. Immunohistochemical analysis was performed in a group of AD patients and compared with that in a control group of healthy subjects. Avidin-biotin immunoperoxidase staining of paraffin-embedded, 4 microm skin sections, with semiquantitative counting of cells labeled with anti-CD3, anti-CD8, anti-CD20, anti-HLA-DR (HLA, human leukocyte antigen), and anti-immunoglobulin E (anti-IgE) primary antibodies, was used. The results of AD skin analysis showed a greater infiltration of CD3+ lymphocytes, especially of CD4+ subtype, compared with CD8+ lymphocytes. AD skin biopsy specimens also showed a higher intraepidermal HLA-DR+ Langerhans' cell count, the presence of HLA-DR on lymphocytes in the dermis, and higher intraepidermal expression of IgE+ cells compared with healthy controls. A statistically significant difference (P < 0.05) was found between the two groups for intradermal and intraepidermal CD3, CD4, and HLA-DR, intradermal CD8, and intraepidermal IgE+ cells. Immunophenotyping was found to be a useful diagnostic method in AD patients.

Coordinate expression of cytokeratins 7 and 20 in feline and canine carcinomas.

Forty-seven feline and 60 canine epithelial tumors were studied to test the coordinate expression of cytokeratin 7 (CK 7) and cytokeratin 20 (CK 20) using commercially available monoclonal antibodies and an avidin-biotin immunoperoxidase staining technique. Previously, the distribution of both cytokeratins was examined in normal tissues from 4 cats and 4 dogs. The pattern of distribution of CK 7 in normal tissues was similar, with minor differences, to that described in humans, whereas the reactivity pattern of CK 20 in cats and dogs was wider than that in humans. The subset of tumors strongly expressing CK 7 and CK 20 included pancreatic adenocarcinomas (100%), transitional cell carcinomas (75%), and endometrial carcinomas (67%) in the cat. None of the canine tumors had this immunophenotype. Feline (50%) and canine (56%) mammary gland carcinomas and canine cholangiocarcinomas (67%) were the only tumors presenting the CK 7 +/CK 20- immunophenotype, whereas the CK 7-/CK 20+ immunophenotype included thyroid carcinomas (100%), intestinal adenocarcinomas (60%), bronchioloalveolar carcinomas (50%), and renal carcinomas (50%) in the cat and intestinal adenocarcinomas (56%), gastric adenocarcinomas (50%), and ovarian carcinomas (50%) in the dog. The CK 7-/CK 20- immunophenotype included the rest of the analyzed tumors. The immunohistochemical evaluation of coordinate expression of both CK 7 and CK 20 in feline and canine carcinomas using monoclonal antibodies provides important information that can help to discriminate among carcinomas from different primary sites and could be particularly helpful in the determination of the primary site of origin of carcinomas presenting as metastatic disease.

Demonstration of leptospiral antigens on tissues using monoclonal antibodies and avidin-biotin peroxidase staining

Glycolipoprotein (GLP) cytotoxin was extracted from Leptospira interrogans serovar canicola. The silver staining profile of GLP subjected to SDS-PAGE under denaturing conditions showed a number of bands in the mol. weight range of 14-66 kDa. Mouse Monoclonal Antibodies (MAbs) IgG3 recognizing a band near to 24 kDa of leptospiral GLP were produced (clone number MGLP-01). The agglutinating property of MAbs was established by microscopic agglutination test (MAT) using 25 different serovars as antigens. Only the homologous serovar was agglutinated by MAbs suggesting that the recognized epitope is a specific surface-exposed antigen. The MAbs were applied to demonstration of leptospiral antigens in tissue damage by avidin-biotin immunoperoxidase staining. Golden hamsters were experimentally infected with a virulent strain of L. interrogans serovar canicola. Histologically kidneys stained by routine hematoxylin and eosin showed changes characterized by injury of tubular epithelial cells leading to acute tubular necrosis (ATN). Typical, well-defined morphologic leptospires or finely granular deposits were found by immunoperoxidase staining near to blood vessels, within inflammatory infiltrates and intraluminal in proximal and distal parts of the nephron. Binding of leptospiral antigens to capillary endothelial cells, tubular epithelial cells and macrophages were also demonstrated. This entails a basis for further studies either in research or in diagnostic histopathology.

A monoclonal antibody to human placental lactogen hormone facilitates isolation of fetal cells from maternal blood in a model system : Latham S.E., Suskin H.A., Petropoulos A., Hawes C.S., Jones W.R., Kalionis B. Department of Obstetrics and Gynaecology, Flinders University of South Australia, Bedford Park, SA 5042, Australia [Prenatal Diagnosis 16(9), 813–821; 1996

Human placental lactogen is one of the major hormones secreted by the placental syncytiotrophoblast anddetected in the maternal circulation. Other sources of this hormone in intrauterine tissues at term have been sought by means of immunohistochemistry and northern analysis. Avidin-biotin immunoperoxidase staining with a specific polyclonal antibody to human placental lactogen showed this hormone to be present in groups of cells at the interface between chorionic cytotrophoblast and decidua parietalis and in some cells of the basal plate in addition to the classic source, the syncytiotrophoblast. Hybridization of polyadenylio-`ribonucleic acid extracted from amnion, chorion, decidua parietalis, basal plate, and placental trophoblast with a radiolabeled 48 mer oligonucleotide and a 540 base pair complementary deoxyribonucleic acid probe to human placental lactogen showed the placental trophoblast to be the major source of human placental lactogen and the extravillous chorion and basal plate to be additional minor sources

Use of immunohistochemistry and polymerase chain reaction for detection of oncornaviruses in formalin-fixed, paraffin-embedded fibrosarcomas from cats

Objective To determine whether there was intralesional infection or expression of FeLV or feline sarcoma virus in suspected vaccine-associated fibrosarcomas in cats. Design Prospective case series. Sample Population 130 suspected vaccine-associated fibrosarcomas from cats and 1 multicentric fibrosarcoma from 1 cat. Procedure Excisional biopsy specimens were fixed in formalin and embedded in paraffin. Expression of FeLV antigen was assessed, using a polyclonal goat anti-FeLV glycoprotein 70 (gp 70) serum and an avidin-biotin immunoperoxidase staining technique. The FeLV genome was detected with a polymerase chain reaction (PCR), using primers targeted to a conserved sequence in the untranslated region of the long terminal repeat (LTR) of the FeLV. Results FeLV gp 70 and LTR sequence were detected in a multicentric fibrosarcoma. All 130 of the suspected vaccine-associated fibrosarcomas were FeLV gp 70 negative on the basis of immunohistochemical test results; 100 fibrosarcomas also were examined by use of PCR and were negative for FeLV LTR region. Clinical Implications Exogenous retroviruses, FeLV, and feline sarcoma virus were not detected in these suspected vaccine-associated fibrosarcomas, using immunohistochemistry and PCR. Additional testing will be required to determine the nature of genomic alterations that are involved in the oncogenesis of vaccine-associated fibrosarcomas in cats. (J Am Vet Med Assoc 1996;209:767–771)

Beta 1 and beta 4 integrin expression in methacarn and formalin-fixed material from in situ ductal carcinoma of the breast.

The integrins are alpha beta heterodimeric transmembrane proteins mediating cell-substratum as well as cell-cell interactions. Previous distribution studies on integrin expression have been limited by the requirement of cryostat sectioned tissues, and consequent poor resolution. We have examined 40 examples of ductal carcinoma in situ (DCIS) for the expression of both beta 1 and beta 4 integrin chains. These showed strong polarized membrane staining of residual myoepithelial cells (correlating with expression of smooth muscle specific actin) and of the basement membrane region with beta 1 and beta 4 antibodies respectively. In 12 out of 40 cases, the DCIS was negative for the beta 1 chain and a variable pattern of reactivity was seen in the remaining cases. The beta 4 chain was detected focally and weakly in the tumour cells of 7/40 DCIS and strongly in one; all of these cases were also positive for the beta 1 chain. Of the 22 cases where co-existent invasion was present, the infiltrating component showed either a similar degree or a diminution of the extent of immunostaining when compared with the in situ component; only one showed enhanced staining (beta 1 only). This study demonstrates that two of the main beta chains, beta 1 and beta 4, can be effectively demonstrated on methacarn and cold (4 degrees C) formalin-fixed tissues by avidin-biotin indirect immunoperoxidase staining and that the results are similar to those achieved using frozen tissue.

Expression and modulation of class I and class II histocompatibility leukocyte antigens on human soft tissue sarcomas

Class I and Class II histocompatibility leukocyte antigens (HLA) play an important role in the antigenic recognition and target cell killing by T-lymphocytes. Their expression and modulation with gamma interferon on human soft tissue sarcomas were investigated. The phenotypic expressions of Class I and Class II HLA were determined by avidin-biotin immunoperoxidase staining using two monoclonal antibodies W6/32 and MEL3, respectively. The present study showed that soft tissue sarcomas frequently had demonstrable Class I HLA and less-frequently expressed Class II HLA: The staining for Class I HLA was more diffuse, and the staining for Class II HLA was generally patchy in appearance. The expressions of two antigens on cultured sarcoma cells were found in accordance with the findings of sarcoma tumors. The expression of Class I antigen was enhanced, and Class II was induced in two cell lines by gamma interferon. The in vitro modulation of HLA with gamma interferon was reversible. Gamma interferon at the testing dose did not have cytotoxic or antiproliferative effects on either cell lines. Through the modulation of HLA on soft tissue sarcomas, gamma interferon may play a role in the clinical management of sarcomas.

Direct visualization of renin-cell distribution in preglomerular vascular trees dissected from rat kidney.

Three methods to visualize directly the distribution of granulated renin-positive cells in vascular trees microdissected from rat kidney were developed. Kidneys were removed from anesthesized rats, hemisectioned, macerated in HCl, and soaked in distilled water for 24-48 h. Cortical preglomerular vascular trees consisting of arcuate and cortical radial arteries and afferent arterioles were microdissected with the aid of a stereomicroscope. Granulated cells can be visualized in three ways. First, under transmitted or incident light observation, granulated cells are readily distinguished from the surrounding smooth muscle cells, because of marked differences in the refractive properties of these two cell types. Second, quinacrine, a fluorescent, intravital stain selective for dense-core granules, can be administered (2 mg/kg iv) to the rat 1 h before nephrectomy. When illuminated with 440-nm light, granulated cells fluorescence strongly at 510 nm. Third, specific immunostaining for renin can be obtained with a polyclonal anti-rat renin antibody and avidin-biotin immunoperoxidase staining in vascular trees subjected to cell permeabilization with Triton. These new techniques permit the direct visualization of the distribution of granulated renin-positive cells in preglomerular vessels under conditions in which the vascular architecture is largely preserved.

The Extracellular Matrix Components Laminin, Fibronectin, and Collagen IV Are Present among the Epithelial Cells Forming Rathke’s Pouch

Cell-matrix interactions probably play a cooperative role with cell-hormone interactions to ensure normal differentiation of the adenohypophysis. The extracellular matrix (ECM) surrounding adult adenohypophysial cells contains laminin but its embryonic development has not been described. This study was carried out to test the hypothesis that adenohypophysial cells are associated with components in the ECM prior to cellular differentiation in the adenohypophysis. Fetuses were removed from Golden Syrian hamsters every 12 h from embryonic days 8.5-14. Coronal and sagittal 5-microns-thick sections of paraplast-embedded embryos were stained for fibronectin, laminin, or collagen IV using avidin-biotin immunoperoxidase staining. The adenohypophysial anlage was observed initially as a group of epithelial cells (Rathke's pouch) in the roof of the stomatodeum in contact with a basement membrane. The basement membrane stained positively for laminin, collagen IV and fibronectin. Lighter staining for laminin, fibronectin and collagen IV was observed between the developing adenohypophysial cells in Rathke's pouch. Proliferative activity was apparent in the antero-inferior region of Rathke's pouch and resulted in the formation of the bulk of the adenohypophysis. Mesenchyme infiltrates the region between the base of Rathke's pouch and the oral epithelium, thus separating the two. The basement membrane surrounding the pouch appears to become discontinuous in the regions of high proliferative activity. These results show that ECM components appear early during the development of adenohypophysial cells prior to their cellular differentiation into hormone-containing cells. This association between ECM components and developing adenohypophysial cells provides the anatomical basis for cell-ECM interactions to influence adenohypophysial development and differentiation.

Hemorrhagic Enteritis Virus Inclusions in Turkey Renal Tubular Epithelium

Commercial turkeys from four Iowa flocks, two Illinois flocks, and three California flocks were submitted to state diagnostic laboratories because of a variety of health problems. The turkeys ranged in age from 5 to 12 weeks, included both hens and toms, and were owned by five different companies. Some flocks had previously been immunized with live hemorrhagic enteritis vaccine, and other flocks were unvaccinated. In all accessions, basophilic intranuclear inclusion bodies were observed in renal tubular epithelium by light microscopy. Transmission electron microscopy showed that the inclusions consisted of densely packed virus particles. The virions were identified as adenoviruses based upon the icosahedral morphology and average particle diameters of 72 nm. Avidin-biotin immunoperoxidase staining of formalin-fixed, paraffin-embedded kidneys was used to identify this adenovirus as hemorrhagic enteritis virus.

Relationship of arterial wall uptake of radiolabeled liposomes to the presence of monocyte/macrophage cells in the hypertensive and atherosclerotic arterial wall

In vivo radiolabeled liposome uptake in 5 sham-operated, 7 coarctation-induced hypertensive, and 8 atherosclerotic arterial walls from New Zealand White rabbits was compared to determine the mechanism of arterial wall uptake of liposomes. Uptake between the three groups was significantly different ( P < 0.001) with a 3-fold difference in uptake between the sham-operated and hypertensive groups and the hypertensive and atherosclerotic groups. Liposome uptake was significantly higher in the atherosclerotic group of animals ( P < 0.05). Avidin-biotin immunoperoxidase staining for monocyte/macrophage cells revealed that liposome uptake increased concomitantly with arterial wall monocyte/macrophage cellular invasion and that liposome localization, determined by autoradiography, paralleled the monocyte/macrophage cellular distribution in both hypertensive and atherosclerotic arterial walls. This study provides the first direct evidence that liposomes can escape from the circulation and enter the diseased arterial wall. Furthermore, it suggests that one possible mechanism of arterial wall uptake of liposomes is via the monocyte/macrophage cell which avidly and preferentially engulfs liposomes and then passively carries them into the arterial wall during hypertensive and atherosclerotic lesion development. Liposomes could potentially be used to carry agents into the arterial wall in the study of arterial wall lesion development.

The Role of Passive Immunity in Bovine Respiratory Syncytial Virus-Infected Calves

The role of passive immunity in bovine respiratory syncytial virus (BRSV) infections in neonatal calves was evaluated. Calves were divided into groups as follows: colostrum-deprived, sham-inoculated; colostrum-deprived, BRSV-inoculated; and colostrum-fed, BRSV-inoculated. Calves were inoculated with a low-passage field isolate of BRSV for 4 consecutive days by a combined respiratory tract route and were euthanized 6 days after receiving the last inoculation. Arterial oxygen tension (Pao2) decreased significantly over time in colostrum-deprived, BRSV-inoculated calves (P less than .01) and was significantly different among treatment groups (P less than .05). A significant decrease in arterial oxygen saturation was observed in this same group over time (P less than .01). Mean percentage of pneumonic lung volume (determined by computer data digitalization) was significantly greater in infected, colostrum-deprived calves compared with the other groups (P less than .01), and BRSV antigen was detected in these calves by avidin-biotin immunoperoxidase staining. Thus, passive immunity derived from colostrum feeding decreased the severity of BRSV infections in calves.

The effects of the antiprogestin mifepristone, in vivo, and progesterone in vitro on prolactin production by the human decidua in early pregnancy

This study investigated the regulatory effect of progesterone on decidual prolactin (dPRL) production during early human pregnancy (6-7 weeks). Patients (n = 7) were treated with the antiprogestin-mifepristone (RU 486; 600 mg single oral dose) for 24-36 h before termination of pregnancy by curettage. Tissue was also obtained from patients without pretreatment in vivo (n = 8) and acted as controls. Decidual tissue was incubated in vitro with and without progesterone and mifepristone for 5 days and the medium changed daily. Prolactin production by decidua parietalis decreased over the period of incubation and was unaffected by addition of progesterone or mifepristone. However, in the group pretreated in vivo with mifepristone, the production of dPRL was markedly lower than in the control group. In contrast, the production of dPRL by decidua capsularis to which trophoblast was attached, was maintained at a constant level over 5 days of culture and was unaffected by pretreatment with mifepristone in vivo or its addition in vitro, or by progesterone. Prolactin was immunolocalized using avidin-biotin immunoperoxidase staining to decidualized cells within the decidua and the intensity of staining was reduced or absent in the decidua parietalis from the mifepristone group compared to controls, but was similar in decidua capsularis in both control and mifepristone groups, in good agreement with the in-vitro production of dPRL. Our findings suggest that the effect of progesterone may be only facilitative, maintaining decidual differentiation, and dPRL production might only be associated with the presence of progesterone-dependent differentiated decidual cells. Apart from progesterone, factors from trophoblast cells can maintain dPRL production during pregnancy.

Immunocytochemical localization and messenger ribonucleicacid concentrations for human placental lactogen in amnion, chorion, decidua, and placenta

Human placental lactogen is one of the major hormones secreted by the placental syncytiotrophoblast and detected in the maternal circulation. Other sources of this hormone in intrauterine tissues at term have been sought by means of immunohistochemistry and northern analysis. Avidin-biotin immunoperoxidase staining with a specific polyclonal antibody to human placental lactogen showed this hormone to be present in groups of cells at the interface between chorionic cytotrophoblast and decidua parietalis and in some cells of the basal plate in addition to the classic source, the syncytiotrophoblast. Hybridization of polyadenylic-(+)ribonucleic acid extracted from amnion, chorion, decidua parietalis, basal plate, and placental trophoblast with a radiolabeled 48 mer oligonucleotide and a 540 base pair complementary deoxyribonucleic acid probe to human placental lactogen showed the placental trophoblast to be the major source of human placental lactogen and the extravillous chorion and basal plate to be additional minor sources.

Murine Monoclonal Antibodies to Human Pancreatic Cancer: Specificity and Sensitivity

Pancreatic carcinoma (n = 7), pancreatitis tissue (n = 4), normal pancreas tissue (n = 5), colonic adenocarcinoma (n = 4) and in vitro human pancreatic cancer cell lines (n = 6) were studied with the murine monoclonal antibodies (MAbs) 3DS2A, AR1-28, AR2-20, Ca19-9 and CA17-1A to determine their immunohistologic specificity and sensitivity for use as radiolabeled diagnostic imaging agents. Using the avidinbiotin-immunoperoxidase staining technique, MAbs 3DS2A and AR1-28 stained 86 and 100% of pancreatic cancer specimens, respectively. MAbs 3DS2A and AR1-28 are suitable agents for use as radiolabeled diagnostic imaging agents in patients with pancreatic cancer.

Heterogeneity of antigen expression in benign and malignant breast and ovarian epithelial cells

Expression of II distinct antigen families has been studied in normal and malignant epithelial cells from breast and ovary by avidin-biotin immunoperoxidase staining of frozen tissue sections. Each of the antigens was expressed in a fraction of the normal and malignant breast tissues from different individuals. Among breast and ovarian cancers, a similar fraction of tumors expressed each of the determinants. An epitope on a 42-kDa glycoprotein was expressed significantly more often by ovarian carcinomas than by benign ovarian epithelium. Several determinants on 66-, 240-kDa or high-molecular-weight proteins or glycoproteins were expressed significantly more often on benign breast epithelium than on normal ovarian epithelium. Substantial heterogeneity in antigen expression was observed among different tumor specimens. Each of 14 epithelial ovarian cancers expressed a distinctive combination of antigens. Among 18 breast cancers, 16 distinct antigenic phenotypes were observed. Interestingly, comparable heterogeneity was observed in the expression of epitopes on benign breast and ovarian epithelium, compatible with the possibility that the monoclonal reagents recognized polymorphic determinants. Substantial variations in antigen expression were also observed among cells within each neoplasm. However, when antibodies against 5 different determinants were used in combination, a majority of cells could be stained intensely in all 13 breast carcinomas tested and more than 95% of tumor cells could be stained in 10 of the 13.

Double labeling of SIgG+ cells harboring a lymphotropic herpesvirus by avidin-biotin complex immunoperoxidase and immunogold-silver staining techniques.

By reversing the usual order of double-staining procedures, we obtained optimal conditions for simultaneous detection of guinea pig lymphotropic herpesvirus (GPHLV) and surface immunoglobulin G-positive (SIgG+) cells in paraffin-embedded tissue sections. Of the different fixatives tested, Bouin's solution gave the best preservation of morphology and cell surface IgG. Double immunolabeling was best achieved when avidin-biotin complex immunoperoxidase (ABC-IP) staining was performed first for detection of intracellular viral antigen, followed by immunogold-silver staining (IGSS) for localization of cell surface IgG.

Cytomegalovirus detection by nonisotopic in situ DNA hybridization and viral antigen immunostaining using a two-color technique

Rapid methods of specific viral diagnosis in formalin fixed, paraffin embedded tissues include identification of viral incusions in routinely stained histologic sections, immunologic staining of viral antigens, and in situ nucleic acid hybridization. To correlate in situ hybridization with immunologic detection methods, sequential two-color staining was used on tissues from 12 patients, each containing characteristic cytomegalovirus (CMV) inclusions, using a biotinylated CMV DNA probe in an avidin-alkaline phosphatase-linked reaction followed by avidin-biotin complex immunoperoxidase staining of CMV antigen. CMV genetic material was seen in all 17 tissues. CMV antigen was detected in 11 of 17 tissues (65%). The DNA hybridization technique provided more intense staining, detected greater numbers of inclusions, and had less background staining than the immunoperoxidase technique. The alkaline phosphatase reaction product was stable through subsequent immunostaining steps, and immunologic reactivity of CMV antigen was not significantly reduced by prior hybridization steps. CMV DNA probe was localized predominantly within cell nuclei, while CMV antigen immunostaining was predominantly cytoplasmic. It was concluded that sequential in situ hybridization and immunocytochemistry can be performed on standard histologic sections. Furthermore, it is likely that the majority of CMV nucleic acid detected by this tissue hybridization technique is unencapsidated, intranuclear viral DNA and not DNA contained within complete CMV nucleocapsids.

Amnion membrane epithelial cells express class I HLA and contain class I HLA mRNA.

Amnion epithelial cells in membranes from term deliveries, which have been reported not to express histocompatibility Ag, were evaluated for HLA by using an avidin-biotin immunoperoxidase staining system and for class I HLA mRNA by Northern blotting and in situ hybridization. There were three major findings from these studies. 1) Amnion cells frequently expressed class I HLA. Three mAb to monomorphic determinants of class I HLA were used: 61D2, PA2.6, and W6/32. 61D2 identified 1 of 8 fresh amnion membranes as class I positive whereas PA2.6 identified 4/8 and W6/32 identified 5/8. 2) Amnion cells contained class I HLA mRNA. RNA extracted from amnion membranes hybridized to a class I HLA probe (pHLA1.1) in Northern blotting. In situ hybridization procedures with pHLA1.1 showed that essentially all amnion cells contained class I HLA mRNA. 3) Levels of class I HLA mRNA in amnion cells could be modulated. Exposure of amnion explants to medium containing IFN-gamma enhanced levels of class I HLA mRNA in amnion cells, whereas epidermal growth factor diminished those levels. The results suggest that amnion cells transcribe class I HLA genes and are capable of synthesizing class I H chains but that expression may be modulated by extrinsic regulatory molecules.