Analysis of radiolabeled CHO cell-derived rHuGM-CSF pharmacokinetics and biodistribution in rhesus monkeys following intravenous and subcutaneous injection

The purpose of these studies was to examine the biodistribution and pharmacokinetics of radiolabeled human CHO cell-derived rHuGM-CSF in normal Rhesus monkeys (Macaca mulatta) following intravenous (i.v.) and subcutaneous (s.c.) injection. A dual radioisotope tracer technique was utilized to monitor the behavior of rHuGM-CSF in vivo. Recombinant HuGM-CSF was radiolabeled with I-123 (a 13.2 h half-life, 140 KeV pure gamma emitting radionuclide detected using gamma scintigraphic imaging) using a mild chloramine T reaction. A separate preparation of rHuGM-CSF radiolabeled with S-35 methionine by bioincorporation in tissue culture was mixed with the I-123-labeled protein, permitting comparison of data obtained from the two radiolabels. Two dose levels of rHuGM-CSF were used for i.v. bolus (15 and 300 μg/kg) and s.c. (10 and 100 μg/kg) studies. The results of these studies demonstrated that the co-administered I-123 rHuGM-CSF and S-35 rHuGM-CSF followed similar blood elimination kinetics after i.v. or s.c. injection. Following i.v. bolus injection, rHuGM-CSF was found to rapidly distribute to all central body cavity high blood flow organs, followed by rapid uptake in the kidneys and elimination in the urine. There were no differences in the pharmacokinetic values obtained for I-123- and S-35-labeled rHuGM-CSF nor for the two dose levels examined. Following, s.c. injection, I-123- and S-35-labeled rHuGM-CSF were found to reach maximal plasma levels after approximately 16 h. The primary route of elimination was the urine. Monkeys previously exposed to rHuGM-CSF were found to have circulating antibodies to rHuGM-CSF. Studies in these animals revealed a significantly altered distribution and clearance of radiolabeled rHuGM-CSF, with the majority of the injected activity being cleared by the liver.     

Nodular hepatocellular carcinoma--treatment with intraarterial injection of I-131 Lipiodol

Twenty four patients with hepatocellular carcinoma who refused surgery or had unresectable tumor ranging 2.5 to 8.0 cm in size were treated with intrahepatic arterial injection of iodine-131-labeled iodized oil (I-131 Lipodol) in an attempt to achieve internal radiation of tumor. 555-2,220 MBq in 3-8 ml of I-131 Lipiodol was injected into the hepatic artery or proximal to the tumor feeding vessel depending on the tumor size. Tumor size reduction was observed in 88.9% of tumor smaller than 4.0 cm in diameter, 65.5% between 4.1 to 6.0 cm, and 25.0% of larger than 6.1cm, respectively. The tumor size reduction was corresponded to the gradual drop of serum AFP levels, decreased uptake on gallium-67 scintigraphy, and devascularization on follow-up angiography. Tumors having significant A-V shunts revealed further tumor growth. Adverse reactions from the treatment include fever, mild abdominal pain, nausea and elevation of transaminases. These have been mild and well-tolerated by the patients. This method was able to provide long term local control without complications related to thyroid, lung, GI tract and bone marrow.     

阴离子长循环脂质体在瘤鼠体内分布和反义显像

建立乳腺癌模型,了解游离的131I-bcl-2/bcl-xlASON(FA)以及阴离子长循环脂质体包裹的131I-bcl-2/bcl-xlASON(NA)在瘤鼠体内组织分布。SD大鼠尾静脉注射N-甲基亚硝基脲溶液,诱导建立乳腺癌模型。NA和FA分别静脉注射后0.5、1、2、3、4、6、12和24 h,断头处死瘤鼠,取其组织器官测量,计算每克组织放射性计数占注入剂量的百分数(%ID/g)。计算瘤鼠肿瘤/血液或肿瘤/肌肉比值。分别静脉注射0.4 mCi NA1、31I-错配序列阴离子长循环脂质体(NS)和131I-无义序列阴离子长循环脂质体(NN)后0.5、1、2、3、6和12 h,进行瘤鼠全身前后位静态显像。MNU致瘤时间为(96±1.2)d,SD大鼠致癌率为70%(90/130),组织学类型为乳腺癌。注射后10 h,NA在瘤鼠肿瘤组织、肝和脾内的分布分别为(6.23±0.23)%ID/g、(12.00±0.26)%ID/g和(18.25±1.33)%ID/g。肿瘤/血液和肿瘤/肌肉比值分别为6.29±0.76和10.55±0.68。NA注射后10 h,肿瘤显示最佳。NS和NN注射组瘤鼠肿瘤显示不清。NA体内清...     

抗人结肠癌单克隆抗体SC3A在荷瘤裸鼠体内的放射免疫定位研究

本文用~(131)I标记自制的抗人结肠癌单克隆抗体SC3A,进行荷人结肠癌裸鼠体内生物学分布和肿瘤的放射免疫显像研究。结果在注射~(131)I饲—SC3A后24～120h,肿瘤部位的放射性均显示出选择性浓聚,以72～120h的影像最为清晰;而注射~(131)I—鼠IgG则呈全身均匀性分布,无肿瘤部位选择性波聚影像。在72h,13种器官的T/NT均大于2,肿瘤LI为6.94,与扫描显像结果吻合。这些都表明SC3A在生物体内对结肠癌具有良好的选择性和导向作用,抗体可对其供临床体内进一步应用提供了依据。     

抗ProGRP(31-98) scFv的131I标记及生物分布研究

目的 研究抗胃泌素释放前体（ProGRP（31-98）单链抗体（scFv）的131I标记方法,并对其标记后的稳定性、免疫活性及生物分布进行分析.方法 采用氯胺T法碘化标记制备131I-anti-ProGRP（31-98）scFv,凝胶柱层析法分离纯化标记产物,利用纸层析法测定标记物的标记率、放化纯度和稳定性,采用细胞结合分析法比较131I-anti-ProGRP（31-98）scFv对小细胞肺癌细胞株NCI-H446和肺腺癌细胞株A549的免疫结合率.将131I-ProGRP（31-98）scFv注射入动物体内,研究其在实验动物体内的分布情况.结果 131I-anti-ProGRP（31-98）标记率为（93.35±0.67）％,标记产物纯化后即刻放化纯度为（98.49±1.21）％.131I-anti-ProGRP（31-98）scFv对人小细胞肺癌NCI-H446和肺腺癌A549细胞株的免疫结合率分别为（85.36±1.45）％和（21.02±2.16）％,且差异有统计学意义（P＜0.05）.131I-anti-ProGRP（31-98）scFv在实验动物体内主要通过肾脏和肝脏代谢,血液清除快.结论 131I-anti-ProGRP（31-98） scFv的标记率高,且有良好的稳定性和免疫活性,在实验动物体内主要通过肝脏和肾脏代谢,血液清除快.     

A new radiopharmaceutical compound (131I-PR81) for radioimmunotherapy of breast cancer: labeling of antibody and its quality control

PR81 is a monoclonal antibody that binds with high affinity to MUC1, which is over expressed on breast and other tumors. The objective of this study was to evaluate the application of this antibody against MUC1 as a radioimmunotherapeutical agent. Monoclonal antibody (PR81) against MUC1 was prepared, characterized, purified, and labeled with 131I. The immunoreactivity of radiolabeled mAb PR81with MUC1 (the native protein), BSA-P20 (a 20 amino acid corresponding the tandem repeat of MUC1) and MCF7 cell line were performed by RIA. In vitro stability of radiolabeled mAb in human serum was determined by thin layer chromatography (TLC). Cell toxicity and in vitro internalization studies were performed with the MCF7 cell line, and the tissue biodistribution of the radioiodinated PR81 was evaluated in normal BALB/c mice at 4, 24 and 48 hrs. The tumor imaging was performed in BALB/c mice with breast xenograft tumors at 24 and 72 hr after the complex injection. The labeling efficiency was found to be 59.9% ± 7.9%. MAb-131I conjugates showed high immunoreactivity towards MUC1 protein, BSA-P20 and MCF7 cell line. In vitro stability of the labeled product in human serum was found to be more than %50 over 24 hr. Cell toxicity and in vitro internalization studies showed that the mAb-131I conjugate inhibited 80% growth of the MCF7 cultured cell lines in vitro in a high concentration and up to %60 of the conjugate internalized after 24 h. Biodistribution studies were performed in normal BALB/c mice at 4, 24 and 48 hrs post-injection and no important accumulation was observed in vital organs. The tumors were visualized with high sensitivity after 24 and 72 hr in radioimmunoscintographical studies. These results show that the new radiopharmaceutical may be considered as a promising candidate for therapy of breast cancer.     

Localization of radiolabeled SM1 monoclonal antibody to small-cell lung cancer tumors in mice

Small-cell carcinoma (SCCL) is an aggressive type of lung cancer. Though it is usually responsive to therapy, be it chemotherapy or radiation, the majority of patients eventually relapse and overall prognosis is dismal. New forms of therapy are, therefore, needed. SM1 monoclonal antibody (MAb) was developed in our laboratory and demonstrated to be highly reactive against SCCL. I125 radiolabeled SM1 antibody was administered intravenously to nude mice bearing SCCL tumor xenografts. The mice were sacrificed, different tissues sampled and tested for uptake of radioactivity five days following antibody injection. There was over a 30 fold increase in localization of labeled antibody to the tumor as compared to muscle tissue. All organs tested showed an insignificant amount of MAb (p = 0.01) including the spleen, which had the highest normal tissue uptake in these experiments. These results demonstrate that SM1 MAb can be successfully targeted to SCCL xenografts. Its potential applications for imaging and therapy of SCCL in man are currently under investigation.     

^125I标记单克隆抗体4E5的制备及其在小鼠体内的分布

目的：探讨放射性核素^125I标记单克隆抗体4E5的方法,观察标记物在正常小鼠体内的生物学分布。方法：采用Iodogen法进行单克隆抗体4E5的Ⅲ标记,标记产物用SephadexG-50分离纯化,三氯醋酸（TCA）法测定标记率和放化纯,并对标记物的稳定性进行分析。取45只昆明小鼠随机分成9组,每只小鼠从尾静脉注入剂量为148KBq／0．2ml的^125I-4E5,分别于注药后5min、15min、30rain及1h、2h、6h、24h、48h、72h各处死一组小鼠,取主要脏器称重并测量其放射性计数,计算各脏器每g组织百分注射剂量率（％ID／g）。结果：”I标记4E5的标记率为（79．24-2．6）％,放射化学纯度为（97．1±1．1）％,比活度为294．5MBq／mg;^125I－4E5加入到血清及PBS中放置1w后,放化纯度仍〉90％;体内分布显示^125I-4E5在小鼠体内主要分布于肝、脾、肾,在血液中清除较快。结论：Iodogen法^125I标记4E5的标记率和放化纯度高,方法简便,标记物的稳定性好;。I-4E5在小鼠体内主要通过肝和肾代谢,血液中清除较快。     

Combined immunohistochemical and autoradiographic analyses of antigen/antibody interactions in tumor xenograft models

A study was conducted to establish optimal conditions which would allow for the simultaneous localization of a carcinoma antigen and its complementary radiolabeled antibody. Immunoperoxidase staining was used to identify the tumor distribution of antigen, while tissue localization of the radiolabeled antibody was identified by autoradiography. The tumor associated glycoprotein-72 (TAG-72) antigen and the high affinity murine monoclonal antibody, CC49 IgG were used as the model antigen/antibody pair. Athymic female mice bearing either CX-1 or LS-174T human colorectal adenocarcinoma xenografts were used as animal/tumor test systems. Experimental mice each received a bolus intravenous injection of the CC49 antibody which was labeled with 125I (specific activity, 0.17 to 0.26 microCi/microgram). Control mice were given a bolus injection of MOPC-21 IgG monoclonal antibody (tumor irrelevant antibody) which was also radiolabeled with 125I (specific activity, 0.24 to 0.35 microCi/microgram). At 24 hours postinjection, all tumors removed, counted for radioactivity, and fixed in formalin. The avidin/biotin immunoperoxidase complex technique was used to identify TAG-72 antigenic sites on slide-mounted tissue sections. Nonradiolabeled CC49 IgG (0.5 micrograms/ml) was used as the specific antigen binding primary antibody in the immunostaining procedures. Nonradiolabeled MOPC-21 IgG (0.5 micrograms/ml) served as the negative control. Immunohistochemically stained tissue sections were coated with photographic emulsion and processed for autoradiographic localization of 125I-CC49 or 125I-MOPC-21. After an optimal exposure time of 6 days, slides were processed and examined under a light microscope. Results of the biolocalization experiment revealed that the % of injected dose/gram of 125I-CC49 in both LS-174T and CX-1 tumors (30.4 +/- 5.2% and 20.6 +/- 5.4%, respectively) were significantly greater (p greater than 0.01) than those for 125I-MOPC-21 (4.9 +/- 0.5% and 5.1 +/- 0.7%, respectively). In both tumor lines from mice injected with 125I-CC49, dense clusters of silver grains were found over those regions which were positive for TAG-72 immunoreactivity. These dual-labeled structures were also found in contact with, or in close proximity to the microvasculature. Tumors from mice which were injected with the control radioconjugate showed a random distribution of silver grains within stromal tissue but no specific localization to TAG-72 positive regions. We conclude that intravenously administered 125I-CC49 IgG localizes specifically to antigen-containing sites in the LS-174T and CX-1 tumor models. The methods described herein should serve as useful tools for the direct study of antigen-antibody interactions in tumor biology.     

抗人肝细胞肝癌单克隆抗体的制备及鉴定

目的 制备高特异性和高亲和力的抗人肝细胞肝癌(HCC)的单克隆抗体(MAb),为肝癌的靶向诊断及治疗提供依据.方法 用人肝细胞肝癌细胞株HepG-2经"尾静脉.脾脏联合方法"免疫BALB/c小鼠.取其脾脏细胞与同源小鼠骨髓瘤细胞SP2/0-Ag14融合,经ABC免疫组化初筛抗体、有限稀释法亚克隆化、染色体分析、免疫组化鉴定抗体特异性、共聚焦显微镜扫描技术(LSCM)进行组织定位、ELISA分析鉴定抗体的亚型及荷人肝癌裸鼠牛物分布等进一步鉴定其生物学特性.结果 (1)获得一株分泌抗人肝细胞肝癌单克隆抗体的杂交瘤;该抗体与肝癌组织结合的特异性高达98.5%(67/68);(2)注射131I-MAb后瘤部位放射性分布有逐渐增加的趋势,血液、肝脏、肾脏和肺脏放射性有逐渐减低的趋势,72 h肿瘤/血液和肿瘤,肝脏比值分别为15.76±3.28和7.23±1.70.结论 成功制备抗人肝细胞肝癌的单克隆抗体,具有较好的肝癌特异性、靶向性,对原发性肝癌有潜在的诊断及治疗作用.     

Radioimmunolocation of a heterotransplanted human choriocarcinoma (BeWo) using monoclonal anti-SSEA-1: pharmacokinetics

Stage-Specific Embryonic Antigen-1 (SSEA-1), originally discovered on mouse teratocarcinomas, has since been found on some human non-seminomatous germ-cell tumors and adenocarcinomas, as well as on some adult mouse and human tissues. A monoclonal antibody to this antigen (anti-SSEA-1; IgM, kappa) was used for radioimmunolocation. Nude mice bearing the human choriocarcinoma BeWo, which is SSEA-1 positive, were injected using a mixture of [131I]anti-SSEA-1 and [125I]MOPC 104E, an unselected myeloma protein of the same heavy-chain isotype. Animals were sacrificed at 24 hour intervals; the radioactive deposition due to both antibodies was determined for both tumors and normal organs. Accumulation of anti-SSEA-1 in the tumor was consistantly rapid and specific, while little accumulation of the unselected myeloma protein occurred. At five days after injection, an average of 3% of the initial dose of specific antibody was retained per gram of tumor; the tumor/blood ratio was 11, tumor/muscle was 80. Gamma-camera imaging allowed ready location of the tumors. Tumors could also be imaged using F(ab')2 antibody fragments.     

Simultaneous detection of immunoglobulin A (IgA) and IgM antibodies against hepatitis E virus (HEV) Is highly specific for diagnosis of acute HEV infection

Serum samples collected from 68 patients (age, mean +/- the standard deviation [SD], 56.3 +/- 12.8 years) at admission who were subsequently molecularly diagnosed as having hepatitis E and from 2,781 individuals who were assumed not to have been recently infected with hepatitis E virus (HEV; negative controls; 52.9 +/- 18.9 years), were tested for immunoglobulin M (IgM) and IgA classes of antibodies to HEV (anti-HEV) by in-house solid-phase enzyme immunoassay with recombinant open reading frame 2 protein expressed in the pupae of silkworm as the antigen probe. The 68 patients with hepatitis E had both anti-HEV IgM and anti-HEV IgA. Among the 2,781 controls, 16 (0.6%) had anti-HEV IgM alone and 4 (0.1%) had anti-HEV IgA alone: these IgA/IgM anti-HEV-positive individuals were not only negative for HEV RNA but lack IgG anti-HEV antibody as well (at least in most of the cases). Periodic serum samples obtained from 15 patients with hepatitis E were tested for HEV RNA, anti-HEV IgM, and anti-HEV IgA. Although HEV RNA was detectable in the serum until 7 to 40 (21.4 +/- 9.7) days after disease onset, both IgM and IgA anti-HEV antibodies were detectable until 37, 55, or 62 days after disease onset in three patients and up through the end of the observation period (50 to 144 days) in 12 patients. These results indicate that detection of anti-HEV IgA alone or along with anti-HEV IgM is useful for serological diagnosis of hepatitis E with increased specificity and longer duration of positivity than that by RNA detection.     

Purification of fibrin-specific monoclonal antibody from ascites fluid by preparative isoelectric focusing

With the increased use of site-directed monoclonal antibodies (MAbs) for the detection and localization of antigens (Ags) in vivo, an efficient, noninjurious MAb purification procedure is essential [1-9]. In this study MAb was purified by both immunoaffinity chromatography (IAFC) and preparative isoelectric focusing (PIEF). For anti-fibrin MAb purified by each method, the purification efficiency, blood clearance, and in vivo localization in thrombi were compared. Blood clearance rates and in vivo localization were determined by a double isotope assay: affinity-purified MAb was labeled with I-125, and PIEF-purified MAb was labeled with I-131. Both were injected intravenously into a dog with an experimentally induced femoral vein thrombus. MAb purified by PIEF had a slightly longer biological T 1/2 resulting in comparably higher thrombus localization. Due to its efficiency, PIEF warrants consideration when purified MAb is desired.     

抗人肝细胞肝癌单克隆抗体的制备及鉴定

目的 制备高特异性和高亲和力的抗人肝细胞肝癌（HCC）的单克隆抗体（MAb）,为肝癌的靶向诊断及治疗提供依据.方法 用人肝细胞肝癌细胞株HepG-2经＂尾静脉.脾脏联合方法＂免疫BALB/c小鼠.取其脾脏细胞与同源小鼠骨髓瘤细胞SP2/0-Ag14融合,经ABC免疫组化初筛抗体、有限稀释法亚克隆化、染色体分析、免疫组化鉴定抗体特异性、共聚焦显微镜扫描技术（LSCM）进行组织定位、ELISA分析鉴定抗体的亚型及荷人肝癌裸鼠牛物分布等进一步鉴定其生物学特性.结果 （1）获得一株分泌抗人肝细胞肝癌单克隆抗体的杂交瘤;该抗体与肝癌组织结合的特异性高达98.5%（67/68）;（2）注射131I-MAb后瘤部位放射性分布有逐渐增加的趋势,血液、肝脏、肾脏和肺脏放射性有逐渐减低的趋势,72 h肿瘤/血液和肿瘤,肝脏比值分别为15.76±3.28和7.23±1.70.结论 成功制备抗人肝细胞肝癌的单克隆抗体,具有较好的肝癌特异性、靶向性,对原发性肝癌有潜在的诊断及治疗作用.     

B-cell hybridoma as intraperitoneal tumor model: correlation between tumor growth and monoclonal antibody production.

Murine B-cell hybridoma cells producing an immunoglobulin G1 (K13), specific for human immunoglobulin kappa chains were inoculated intraperitoneally in mice. After intraperitoneal injection of 10(6) K13 hybridoma cells, superficial intraperitoneal implants and ascites developed, resulting in death after 10 +/- 3 days (mean +/- SD). An immunoradiometric assay was developed to measure K13 in murine blood, ascites and culture supernatant. The assay utilized polymer beads coated with human immunoglobulin G. The amount K13 bound to the particles was measured with a 125I-labelled monoclonal rat antibody (LO-MG1-13) specific for mouse IgG1. The assay could be used over a wide working range (2-500 micrograms/l). Kinetic studies suggested that about 10(5) secreting cells were required for detection of K13 in blood. After injection of 10(6) cells, K13 was measurable in blood 1 day later in all animals. Nine of 33 mice injected with 10(5) or less cells survived, and initially showed rising K13 blood levels followed by decreasing blood levels. In conclusion, a close relationship was established between i.p. growth of the hybridoma K13 cell line and the MAb blood levels. The basic concepts of this assay can readily be adopted for other clones with the limitation that pure antigen is needed for solid phase extraction of the MAb from mouse blood.     

In vivo and in vitro binding of iodinated monoclonal antibody A2B5 to RIN insulinoma cells

Monoclonal antibody A2B5 reacts with the cell surface of a series of amine precursor uptake decarboxylation (APUD) cells and their tumors in many vertebrate species including chicken, rat, mouse, and man. We have studied the in vivo and in vitro binding of iodinated monoclonal antibody A2B5 to rat insulinoma cells. In vitro, radiolabeled A2B5 binds specifically to RINm5F insulinoma cells and the binding of 125I-A2B5 is inhibited by unlabeled A2B5 or a ganglioside extract of RINm5F cells. In vivo, scintigrams taken Day 0 to Day 5 after injection of 131I-labeled A2B5 showed a striking localization of 131I-A2B5 in transplanted RIN tumors grown in syngeneic rats. Other control radiolabeled monoclonal antibodies did not concentrate in the tumors. 131I-labeled A2B5 did not concentrate in other transplantable tumors (colon adenocarcinoma, osteosarcoma, renal cell carcinoma, and bladder transitional cell carcinoma) grown in nude mice. The tumor/blood ratio detected 5 days after antibody injection, was approximately two to 12 times higher in the insulinoma compared to other organs and only in the insulinoma did 131I-A2B5 show a higher concentration than control antibody 125I-P3X63.     

Biodistribution and pharmacokinetics of recombinant, human 125I-interleukin-2 in mice

The pharmacokinetics and biodistribution of radioiodinated recombinant interleukin-2 (125I-IL-2) was studied after either intravenous (i.v.) or intraperitoneal (i.p.) injection into C57BL/6 mice. Beta-lactoglobulin radiolabeled with 131I served as a control protein. After i.v. injection, 125I-IL-2 preferentially accumulated in the liver and spleen. Liver accumulation was fast, peaking at 5 min, and was followed by rapid clearance. Spleen accumulation was slightly slower, peaking at 15 min. Blood values 1 min after i.v. injection were 22-34% of the injected doses (I.D.)/gram. These values declined quickly over the next hour. In contrast, after i.p. administration no organ showed specific uptake of 125I-IL-2. Blood values after i.p. injection were essentially constant over 3 h and were greater and more sustained than after i.v. administration. Kidney values for both 125I-IL-2 and 131I-beta-lactoglobulin, after either i.v. or i.p. injection, indicated that the major route of clearance for both compounds was rapid loss through the kidneys.     

Cytokine administration alters the distribution of activated lymphocytes to the lung

The effects of intraperitoneal injections of recombinant interleukin-1 alpha (IL-1; 250,000 U/day), interleukin-2 (IL-2; 50,000 units/day), interferon-gamma (IFN-gamma; 50,000 U/day) and tumor necrosis factor-alpha (TNF; 100,000 U/day), on the biodistribution of concanavalin A (Con A)-activated, indium-111-labeled lymphocytes were evaluated in BALB/c mice. Syngeneic spleen cells were activated for 48 h in medium with Con A (5 micrograms/ml) and maintained in culture for 72 h in IL-2 (1,000 U/ml). Groups of 12 mice were treated for 4 days with either one of the cytokines or saline. On day 4, mice received 10(7) lymphocytes (3-5 mu Ci) intravenously. Mice were sacrificed at 4 and 24 h following injection and the percent of administered dose per organ was determined. TNF and IL-1 produced a significant increase in lung uptake of radiolabeled lymphocytes at 4 and 24 h, whereas IL-2 and IFN-gamma decreased uptake at both time points. IL-1 increased uptake by liver at 4 and 24 h while IL-2 increased uptake only at 4 h. We conclude that the distribution of activated lymphocytes following adoptive transfer is altered by cytokines. This finding may have important implications for cell delivery during adoptive immunotherapy.     

A rat monoclonal antibody specific for murine type 1 pneumocytes.

A rat monoclonal antibody (MAb), 411-52, that binds specifically to murine pulmonary alveolar type 1 cells was developed. The cell-binding specificity of MAb 411-52 was assessed by light microscopy on immunoperoxidase-labeled tissue sections, electron microscopy on immunogold-labeled tissue blocks, and by flow cytometric analysis and fluorescence-activated cell sorting of immunofluorescently labeled cells enzymatically dissociated from murine lungs. The epitope recognized by MAb 411-52 was first detected in immunoperoxidase-stained sections of neonatal lungs of mice approximately 3 weeks after birth. In adult mice, the MAb 411-52-directed, immunoperoxidase-staining pattern was uniform throughout the lung parenchyma, was restricted to the luminal surfaces of alveoli, and was absent from type 2, endothelial, and interstitial cells, as well as from the epithelial cells of conducting airways. Electron microscopic analysis of immunogold-labeled lung tissue confirmed the type 1 cell binding specificity of MAb 411-52. Analysis by multiparameter, laser flow cytometry indicated that MAb 411-52 binds to 4.6 +/- 0.5% (mean +/- SD) of enzymatically dissociated cells from the lungs of normal adult mice. The absence of immunogold-labeling of type 2 cells suggested that the epitope recognized by MAb 411-52 might be a differentiation marker for the type 1 cell phenotype. With this MAb and standard immunohistochemical techniques, it is possible to visualize directly type 1 cells in paraffin sections.     

Kinetics of the decline phase of the primary response to human serum albumin in the bird.

After the intravenous injection of a wide range of doses of human serum albumin (50 micrograms--10 mg) the biosynthesis of antibody maintained constant kinetics although the peak titre increased with the dose of antigen throughout this range. After the rapid rise to a sharp peak at day 7, the antibody levels in the decline period (7-17 days) manifested exponential decay and a constant half-life of 2.2 days which approximated to that observed with passively administered 131I-labelled 7S chicken Ig. It was concluded that after the antibody peak no further antibody production occurs and the switching-off of this antibody response must begin about 3 days before the time of the peak: counts of antibody-containing plasmacytes in the spleen were maximum at day 4. The rate of antibody catabolism and the timing of switch-off of antibody production appeared to be independent of either the dose of antigen injected or the level of antibody at the peak. The mechanisms of the switch-off are discussed.