Functional and ontogenetic analysis of murine CD45Rhi and CD45Rlo CD4+ T cells

CD4+ murine T cell clones, TH1 and TH2, can be distinguished by both functional responses and by their patterns of lymphokine secretion. Recently, a mAb, 23G2, which reacts with a subset of CD45 molecules (CD45R), has been reported to bind differentially to clones of TH1 and TH2 cells. In the present study, normal splenic T cells were analyzed for differences in 23G2-reactivity and were separated into two populations based on their density of CD45R (CD45Rhi and CD45Rlo). The CD45Rhi cells secrete more IL-2 than IL-4 after stimulation in vitro; the reverse is true for the CD45Rlo cells. Because neither population secretes only IL-2 or IL-4, we were unable to classify cells as TH1 or TH2. In vivo and in vitro analyses of the CD45Rhi and CD45Rlo cells suggest a lineage relationship between the two subsets that correlates with the degree of Ag exposure and the state of maturation of the mice. In newborn mice and mice raised under sterile conditions, splenic CD4+ T cells are predominantly CD45Rhi. Under conditions of increased antigenic exposure and maturation of the mice, CD45Rlo cells develop; after long term priming in vivo, the majority of specific Ag-reactive cells are CD45Rlo. Adoptive transfer studies using BALB/c nu/nu recipients demonstrate that CD45Rhi cells become CD45Rlo cells and that the recall response (IgG) to specific Ag is mediated by CD45Rlo cells. Taken together, these data indicate that the level of expression of CD45R on CD4+ T cells distinguishes virgin (CD45Rhi) from primed/memory (CD45Rlo) T cells in normal mice.

Long ascending unmyelinated primary afferent axons in the rat dorsal column: immunohistochemical localizations

The present study demonstrates a significant number of calcitonin gene-related peptide (CGRP) immunolabeled unmyelinated axons in the C3 fasciculus gracilis of the rat. Approximately 88% of these axons are lost following dorsal rhizotomies from midthoracic levels caudally. Assuming that CGRP labels primary afferent axons, these findings support the hypothesis that there are significant numbers of long ascending unmyelinated primary afferent axons in the dorsal columns of the rat. If these findings can be generalized, they may have clinical import.

Adrenergic fibers in the spinal cord of the monkey: light and electron microscopic study

The adrenergic innervation of the monkey (Macaca fascicularis) thoracic spinal cord was examined by means of peroxidase-antiperoxidase immunohistochemical method using antisera directed phenylethanolamine N-methyl transferase (PNMT). At light microscopic level the PNMT-positive profiles are seen as brown granules, presumably axon terminals, or varicose fibers. They are localized in the intermediolateral nucleus, central gray and the intermediate gray which connects the two. Occasional fibers are seen in ventral and dorsal horns. The descending adrenergic fiber tract is found in the lateral margin of the lateral funiculus. At electron microscopic level, the PNMT-positive presynaptic profiles exhibit densely packed small clear vesicles, a few large dense core vesicles and numerous mitochondria. They make synaptic contact with dendritic profiles (97%) and somatic profiles (3%) and demonstrate either symmetric or asymmetric synaptic specialization. The descending adrenergic fiber tract consists mainly of unmyelinated fibers and is located in the ventral half of the lateral funiculus.

Vasoactive intestinal polypeptide (VIP) immunoreactivity in the ependymal cells of the rat spinal cord

Vasoactive intestinal polypeptide (VIP) was demonstrated immunohistochemically in the entire ependymal and subependymal cells in all levels (cervical: C, thoracic: T, lumbar: L and sacral: S) of normal adult rat spinal cord. The VIP-immunoreactive basal processes from the apical ependymal cells coursed dorsally or ventrally along the median plane and reached the pia mater of the dorsal and ventral median septa. Many VIP-immunoreactive basal processes terminated on the blood vessels in the neuropil around the central canal. A few microvilli of the ependymal cells that project into the central canal also demonstrated intense VIP immunoreactivity. These observations suggest that ependymal cells may be involved in the modulation of VIP levels in the cerebrospinal fluid and regulation of vascular tone of the blood vessels in the spinal cord.

The effects of dorsal rhizotomy and spinal cord isolation on calcitonin gene-related peptide-labeled terminals in the rat lumbar dorsal horn

In the present study, the origin of calcitonin gene-related peptide (CGRP) to the dorsal horn in the rat lumbar spinal cord is investigated. CGRP immunoreactivity is examined following multiple unilateral and bilateral dorsal rhizotomies and isolated cord preparations (spinal cords are isolated by transecting the cord in two places and cutting all dorsal roots between the transections). Seven to 11 days after surgery, unilateral multiple dorsal rhizotomies result in a drastic decrease in CGRP-stained terminals on the operated side; following bilateral dorsal rhizotomies and isolated cord preparations, one or two CGRP varicosities remain in the dorsal horn in each section. The numbers of CGRP-immunostained varicosities observed in the latter two preparations are not significantly different, suggesting that few if any axons descending from the brain contribute to the CGRP terminal population in the spinal cord dorsal horn. Based on these data, we hypothesize that dorsal root ganglion cells are the only source of CGRP to the rat lumbar dorsal horn.

Comparison of three recombinant murine leukemia viruses carrying the v-src oncogene of avian sarcoma virus: differences in in vitro transformation and in vivo pathogenicity

We previously described a recombinant Moloney murine leukemia virus (Mo-MuLV) carrying the v-src oncogene, Mo-MuLV(src). Mo-MuLV(src) encodes a gag-src fusion protein, transforms cells in culture, and induces fibrosarcomas in vivo. To compare transforming properties of the gag-src fusion protein to pp60src encoded by Rous sarcoma virus, we constructed a new recombinant virus, Mo-MuLV(+ src). Mo-MuLV(+ src) encodes pp60src in the context of Mo-MuLV. Cells transformed by Mo-MuLV(+ src) were round and formed colonies in soft agar, whereas Mo-MuLV(src)-infected cells were fusiform and did not grow in suspension. Thus, the extent of transformation induced by Mo-MuLV(+ src) was greater than that induced by Mo-MuLV(src). Subcutaneous inoculation of either virus into neonatal NIH Swiss mice resulted in fibrosarcomas at the site of injection. Further studies indicated that tumors induced by Mo-MuLV(+ src) grew rapidly but rarely metastasized. In contrast, tumors induced by Mo-MuLV(src) grew somewhat more slowly but metastasized with a high frequency (60%). These viruses may provide a useful model system for tumor metastasis. Another src-containing virus was also studied, MRSV (constructed by Anderson and Scolnick). MRSV also encodes pp60src but in the context of amphotropic MuLV. When injected intravenously into six-week-old mice, MRSV induced splenomegaly and spleen foci but no solid tumors, as reported previously. In contrast, Mo-MuLV(src)-induced fibrosarcomas mostly in the spleen under the same inoculation protocol. These results suggest that the v-src oncogene was the major pathogenic determinant in neonatal mice for all three src-containing viruses; however, variations in the nature of the transforming protein modulated the behavior of the induced tumors. In adult mice, greater differences in pathogenicity were observed.

Effect of B cell stimulatory factor-1 (interleukin 4) on Fc epsilon and Fc gamma receptor expression on murine B lymphocytes and B cell lines

Culture of murine splenic B cells with interleukin 4 (IL-4) caused the up-regulation of the lymphocyte Fc receptor for immunoglobulin E (IgE) (Fc epsilon R) over a similar dose range as required for Ia up-regulation. However, the expression level of the Fc receptor for immunoglobulin G (Fc gamma R) did not increase, rather IL-4 caused a slight but consistent decrease in the Fc gamma R level on the B cells. Fc epsilon R+ B hybridoma cells also responded to IL-4 by exhibiting increased Fc epsilon R expression; with the hybridoma cells Fc gamma R levels were unaffected. IL-4 caused an increase in the number of Fc epsilon R per cell and the highest levels of expression were obtained by having both IgE and IL-4 present in the culture. The specificity of the increase was demonstrated by blocking IL-4-mediated actions with monoclonal anti-IL-4 (11B11). Experiments following the incorporation of [35S]methionine into the Fc epsilon R demonstrated that IL-4 increased the rate of Fc epsilon R biosynthesis; this provides an explanation for the IL-4-induced increase in Fc epsilon R expression. IL-4, unlike IgE, had no effect on the rate of degradation of the Fc epsilon R. Interferon-gamma (IFN-gamma) totally abrogated IL-4-mediated Fc epsilon R up-regulation; at the same concentration of IFN-gamma Ia up-regulation is also suppressed, although not as effectively. IFN-gamma was shown to directly suppress Fc epsilon R synthesis, thereby explaining the inhibitory action on Fc epsilon R levels. Finally, it was shown that 11B11 inhibited the increased expression of Fc epsilon R on B cells obtained from mice during the early, but not the late, stages of Nippostrongylus brasiliensis infection. This latter finding suggests that the high Fc epsilon R levels seen early in parasite infections are dependent upon IL-4. The results overall provide further insight into the biologic activities of IL-4.

Effect of B cell stimulatory factor-1 (interleukin 4) on Fc epsilon and Fc gamma receptor expression on murine B lymphocytes and B cell lines

Culture of murine splenic B cells with interleukin 4 (IL-4) caused the up-regulation of the lymphocyte Fc receptor for immunoglobulin E (IgE) (Fc epsilon R) over a similar dose range as required for Ia up-regulation. However, the expression level of the Fc receptor for immunoglobulin G (Fc gamma R) did not increase, rather IL-4 caused a slight but consistent decrease in the Fc gamma R level on the B cells. Fc epsilon R+ B hybridoma cells also responded to IL-4 by exhibiting increased Fc epsilon R expression; with the hybridoma cells Fc gamma R levels were unaffected. IL-4 caused an increase in the number of Fc epsilon R per cell and the highest levels of expression were obtained by having both IgE and IL-4 present in the culture. The specificity of the increase was demonstrated by blocking IL-4-mediated actions with monoclonal anti-IL-4 (11B11). Experiments following the incorporation of [35S]methionine into the Fc epsilon R demonstrated that IL-4 increased the rate of Fc epsilon R biosynthesis; this provides an explanation for the IL-4-induced increase in Fc epsilon R expression. IL-4, unlike IgE, had no effect on the rate of degradation of the Fc epsilon R. Interferon-gamma (IFN-gamma) totally abrogated IL-4-mediated Fc epsilon R up-regulation; at the same concentration of IFN-gamma Ia up-regulation is also suppressed, although not as effectively. IFN-gamma was shown to directly suppress Fc epsilon R synthesis, thereby explaining the inhibitory action on Fc epsilon R levels. Finally, it was shown that 11B11 inhibited the increased expression of Fc epsilon R on B cells obtained from mice during the early, but not the late, stages of Nippostrongylus brasiliensis infection. This latter finding suggests that the high Fc epsilon R levels seen early in parasite infections are dependent upon IL-4. The results overall provide further insight into the biologic activities of IL-4.

The murine lymphocyte receptor for IgE. IV. The mechanism of ligand-specific receptor upregulation on B cells

Rodent B cells respond to culture with IgE by increasing their IgE-specific Fc receptors (Fc epsilon R). The mechanism of this upregulation was characterized on Fc epsilon R+ murine B cell hybridoma lines. Measurements of [35S]methionine incorporated into the Fc epsilon R over time indicated that IgE did not appreciably increase the rate of Fc epsilon R synthesis. In contrast analysis of Fc epsilon R decay from surface radioiodinated B hybridoma cells demonstrated that IgE acted to slow the rate of Fc epsilon R degradation. Very little endocytosis of monomeric IgE was seen; this, combined with the observation that lysomotropic agents failed to inhibit Fc epsilon R degradation suggested that decay occurs at the cell surface. A soluble receptor immunoassay was developed, using monoclonal anti-Fc epsilon R, and this assay demonstrated that cell-bound IgE inhibited the release into the culture media of soluble immunoreactive Fc epsilon R. Examination of the soluble Fc epsilon R by SDS-PAGE after isolation with monoclonal anti-Fc epsilon R demonstrated that it was 10,000 m.w. smaller than the cell-associated Fc epsilon R. IgE affinity columns failed to bind the Fc epsilon R fragment, indicating that the ligand binding activity was largely lost. Thus this study demonstrated that IgE-dependent Fc epsilon R induction on B cells occurs because IgE upon binding to the B cell surface, inhibits the proteolytic cleavage and release of the Fc epsilon R into the surrounding medium, and it is this inhibition of degradation that causes the higher Fc epsilon R levels.

The murine lymphocyte receptor for IgE. IV. The mechanism of ligand-specific receptor upregulation on B cells

Rodent B cells respond to culture with IgE by increasing their IgE-specific Fc receptors (Fc epsilon R). The mechanism of this upregulation was characterized on Fc epsilon R+ murine B cell hybridoma lines. Measurements of [35S]methionine incorporated into the Fc epsilon R over time indicated that IgE did not appreciably increase the rate of Fc epsilon R synthesis. In contrast analysis of Fc epsilon R decay from surface radioiodinated B hybridoma cells demonstrated that IgE acted to slow the rate of Fc epsilon R degradation. Very little endocytosis of monomeric IgE was seen; this, combined with the observation that lysomotropic agents failed to inhibit Fc epsilon R degradation suggested that decay occurs at the cell surface. A soluble receptor immunoassay was developed, using monoclonal anti-Fc epsilon R, and this assay demonstrated that cell-bound IgE inhibited the release into the culture media of soluble immunoreactive Fc epsilon R. Examination of the soluble Fc epsilon R by SDS-PAGE after isolation with monoclonal anti-Fc epsilon R demonstrated that it was 10,000 m.w. smaller than the cell-associated Fc epsilon R. IgE affinity columns failed to bind the Fc epsilon R fragment, indicating that the ligand binding activity was largely lost. Thus this study demonstrated that IgE-dependent Fc epsilon R induction on B cells occurs because IgE upon binding to the B cell surface, inhibits the proteolytic cleavage and release of the Fc epsilon R into the surrounding medium, and it is this inhibition of degradation that causes the higher Fc epsilon R levels.

Structural alterations in the long terminal repeat of an acquired mouse mammary tumor virus provirus in a T-cell leukemia of DBA/2 mice

ML, a transplantable T-cell leukemia of DBA/2 mice, expresses the gag and env gene products of the murine mammary tumor virus (MuMTV). Analysis of the genomic DNA of ML cells using the restriction enzyme HindIII and hybridization with MuMTV-specific probes revealed that the ML cells contained two or more newly integrated MuMTV proviruses (ML-MuMTV). Further analysis of these proviruses with a combination of Mspl and Pstl enzymes showed that the long terminal repeat (LTR) (ML-MuMTV LTR) of the ML-MuMTV provirus(es) was structurally different from the LTRs of both exogenous and endogenous MuMTV proviruses of DBA/2 mice. In order to characterize the nature of the structural alterations in the ML-MuMTV LTR, we cloned a 4.0-kb HindIII fragment containing the 3' half of an acquired provirus. Sequence analysis of the ML-MuMTV LTR of this acquired provirus revealed a deletion of a 387-bp segment that maps between the 5' nucleotide 616 and the 3' nucleotide 1003 of the normal MuMTV LTR and duplication of a 102-bp fragment that mapped between 514 and 616. In addition to two point mutations in the direct repeat, the proviral ML-MuMTV LTR has also acquired 9- and 7-bp segments at the 5' and 3' sites of the duplicated 102-bp segment, respectively. Since direct repeats in the U3 regions of a number of LTRs have been found to be associated with enhancer function, we examined the enhancer function of the U3 region sequences of the ML-MuMTV LTR using enhancer-dependent transient expression assay of chloramphenicol acetyltransferase (CAT) gene in NIH 3T3 cells. Our studies have shown that the U3 region sequences of the rearranged ML-MuMTV LTR have the ability to enhance the expression of the CAT gene 12- to 15-fold more than the U3 region sequences from the normal MuMTV LTR. The presence of a direct repeat in the ML-MuMTV LTR and its ability to enhance the transcription of adjacent genes is analogous to the LTRs of certain murine leukemia viruses.

Characterization of a monoclonal antibody directed against the murine B lymphocyte receptor for IgE

A rat hybridoma producing a high-affinity IgG2a monoclonal antibody (B3B4) directed against against the murine lymphocyte IgE receptor (Fc epsilon R) was established by using purified Fc epsilon R from Fc epsilon R+ murine hybridoma B cells as immunogen. The monoclonal and polyclonal anti-Fc epsilon R inhibited the binding of IgE to the murine lymphocyte Fc epsilon R and were also used to isolate the Fc epsilon R. B3B4 specifically recognized only the 49-Kd Fc epsilon R on murine B lymphocyte as determined by immunoprecipitation and SDS-PAGE analysis. In addition to its reaction with intact Fc epsilon R, B3B4 also recognized Fc epsilon R fragments that were present in the culture media of Fc epsilon R+ hybridoma cells. The predominant fragments isolated were 38 Kd and 28 Kd by SDS-PAGE analysis. When tested for reactivity with other cell types, B3B4 was highly specific for murine B lineage cells in that it did not significantly react with Fc epsilon R on macrophages and T cells and, in addition, did not react with the high affinity mast cell Fc epsilon R. B3B4 completely blocked IgE rosetting, and a reciprocal inhibition of binding was seen in a dose-dependent fashion between IgE and B3B4, indicating a close proximity of the IgE and B3B4 binding sites. Saturation binding analysis indicated that the Fab' fragment of B3B4 bound to twice as many sites/cell as IgE, suggesting that there are two identical B3B4 determinants per 49-Kd Fc epsilon R or that the IgE binding site is formed by the association of at least two 49-Kd Fc epsilon R. However, unlike IgE, neither B3B4 nor F(ab')2-B3B4 nor Fab'-B3B4 were very effective in causing Fc epsilon R upregulation on murine hybridoma B cells; in fact, B3B4 prevented this upregulation when added in combination with IgE. These results suggest that a site-specific interaction provided only by IgE may be essential for ligand-specific upregulation. Both polyclonal and monoclonal antibodies will be useful in further studies concerning the functional relationship between the membrane Fc epsilon R and the soluble Fc epsilon R fragments.

Characterization of a monoclonal antibody directed against the murine B lymphocyte receptor for IgE

A rat hybridoma producing a high-affinity IgG2a monoclonal antibody (B3B4) directed against against the murine lymphocyte IgE receptor (Fc epsilon R) was established by using purified Fc epsilon R from Fc epsilon R+ murine hybridoma B cells as immunogen. The monoclonal and polyclonal anti-Fc epsilon R inhibited the binding of IgE to the murine lymphocyte Fc epsilon R and were also used to isolate the Fc epsilon R. B3B4 specifically recognized only the 49-Kd Fc epsilon R on murine B lymphocyte as determined by immunoprecipitation and SDS-PAGE analysis. In addition to its reaction with intact Fc epsilon R, B3B4 also recognized Fc epsilon R fragments that were present in the culture media of Fc epsilon R+ hybridoma cells. The predominant fragments isolated were 38 Kd and 28 Kd by SDS-PAGE analysis. When tested for reactivity with other cell types, B3B4 was highly specific for murine B lineage cells in that it did not significantly react with Fc epsilon R on macrophages and T cells and, in addition, did not react with the high affinity mast cell Fc epsilon R. B3B4 completely blocked IgE rosetting, and a reciprocal inhibition of binding was seen in a dose-dependent fashion between IgE and B3B4, indicating a close proximity of the IgE and B3B4 binding sites. Saturation binding analysis indicated that the Fab' fragment of B3B4 bound to twice as many sites/cell as IgE, suggesting that there are two identical B3B4 determinants per 49-Kd Fc epsilon R or that the IgE binding site is formed by the association of at least two 49-Kd Fc epsilon R. However, unlike IgE, neither B3B4 nor F(ab')2-B3B4 nor Fab'-B3B4 were very effective in causing Fc epsilon R upregulation on murine hybridoma B cells; in fact, B3B4 prevented this upregulation when added in combination with IgE. These results suggest that a site-specific interaction provided only by IgE may be essential for ligand-specific upregulation. Both polyclonal and monoclonal antibodies will be useful in further studies concerning the functional relationship between the membrane Fc epsilon R and the soluble Fc epsilon R fragments.

Synthesis and regulation of the IgE receptor on B lymphocyte cell lines

The synthesis and ligand-dependent regulation of the lymphocyte receptor for IgE (Fc epsilon R) has been studied. Using murine Fc epsilon R+ cell lines, a 44-kilodalton 35S-methionine-labeled Fc epsilon R precursor was isolated by immunoaffinity chromatography. In contrast to the final processed 49-kilodalton Fc epsilon R, this precursor cannot be isolated from IgE affinity columns, indicating the importance of this processing in the function of the Fc epsilon R. The IgE-mediated Fc epsilon R upregulation was also studied and it was demonstrated that the degradation rate of the Fc epsilon R was dramatically slowed by ligand occupation of the Fc epsilon R. This degradation involves the cell surface-mediated release of a 38-kilodalton Fc epsilon R fragment that can be isolated using monoclonal anti-Fc epsilon R antibodies. Thus, these results demonstrate that posttranslational processing is required for the lymphocyte receptor to gain significant IgE-binding capacity; once acquired its degradation is slowed by occupation of the Fc epsilon R with ligand. At least in the rodent model system, this slowing of the degradation helps explain the increased Fc epsilon R levels seen in the presence of high IgE levels.

Murine B cell hybridomas bearing ligand-inducible Fc receptors for IgE

Interest in the regulation of IgE synthesis has generated investigation of low-affinity Fc receptors for IgE (Fc epsilon R) and the related immunoregulatory IgE-binding factors. In an effort to facilitate biochemical analysis of the B lymphocyte Fc epsilon R, hybridoma technology has been used to create stable cell lines that maintain Fc epsilon R in high numbers. Fusion of the HAT-sensitive B lymphoma, M12.4.5, with murine B cells from Nippostrongylus brasiliensis infected BALB/c mice led to the formation of hybrid cells of B cell phenotype, all of which were Fc epsilon R+, including several that had greater than 50,000 Fc epsilon R/cell. The Fc epsilon R on these cells were biochemically identical to the Fc epsilon R on normal B cells with respect to binding affinity (approximately equal to 10(8) M-1), m.w. (49,000), and tryptic peptides. Each hybridoma cell line specifically increased its Fc epsilon R level between twofold and fourfold when cultured with rat or mouse IgE. Additional studies demonstrated that the increased IgE binding ability was due to an increase in receptor number rather than an affinity change, and the Fc epsilon R increase was seen on the entire cell population. Dose studies indicated that oligomeric IgE was 10-fold more effective than monomeric IgE in causing upregulation, and the effective concentrations required indicated that induction occurred only if IgE was present in saturating concentrations. Upon addition of IgE, peak Fc epsilon R levels were reached after 15 to 20 hr of culture; blocking protein synthesis with cycloheximide largely blocked the increase in Fc epsilon R levels. Additionally, the inductive signal IgE must constantly be present to maintain upregulated Fc epsilon R levels in that its removal from the culture resulted in a rapid decline of Fc epsilon R from induced to normal levels. Because Fc receptor upregulation is important to several systems describing Ig isotype-specific regulation, the ability to examine such receptor upregulation at a clonal level should aid in discerning the role of the Fc epsilon R in the regulation of IgE antibody synthesis.

Murine B cell hybridomas bearing ligand-inducible Fc receptors for IgE

Interest in the regulation of IgE synthesis has generated investigation of low-affinity Fc receptors for IgE (Fc epsilon R) and the related immunoregulatory IgE-binding factors. In an effort to facilitate biochemical analysis of the B lymphocyte Fc epsilon R, hybridoma technology has been used to create stable cell lines that maintain Fc epsilon R in high numbers. Fusion of the HAT-sensitive B lymphoma, M12.4.5, with murine B cells from Nippostrongylus brasiliensis infected BALB/c mice led to the formation of hybrid cells of B cell phenotype, all of which were Fc epsilon R+, including several that had greater than 50,000 Fc epsilon R/cell. The Fc epsilon R on these cells were biochemically identical to the Fc epsilon R on normal B cells with respect to binding affinity (approximately equal to 10(8) M-1), m.w. (49,000), and tryptic peptides. Each hybridoma cell line specifically increased its Fc epsilon R level between twofold and fourfold when cultured with rat or mouse IgE. Additional studies demonstrated that the increased IgE binding ability was due to an increase in receptor number rather than an affinity change, and the Fc epsilon R increase was seen on the entire cell population. Dose studies indicated that oligomeric IgE was 10-fold more effective than monomeric IgE in causing upregulation, and the effective concentrations required indicated that induction occurred only if IgE was present in saturating concentrations. Upon addition of IgE, peak Fc epsilon R levels were reached after 15 to 20 hr of culture; blocking protein synthesis with cycloheximide largely blocked the increase in Fc epsilon R levels. Additionally, the inductive signal IgE must constantly be present to maintain upregulated Fc epsilon R levels in that its removal from the culture resulted in a rapid decline of Fc epsilon R from induced to normal levels. Because Fc receptor upregulation is important to several systems describing Ig isotype-specific regulation, the ability to examine such receptor upregulation at a clonal level should aid in discerning the role of the Fc epsilon R in the regulation of IgE antibody synthesis.

Characterization of the low-affinity receptor for IgE on murine B cells by using membrane impermeant cross-linking reagents

The murine B lymphocyte receptor for the Fc portion of IgE (Fc epsilon R) was further characterized by using the membrane impermeable cross-linking reagents 3,3'-dithiobis-(sulfosuccinimidyl) proprionate (DTSSP) and bis-(sulfosuccinimidyl) suberate (BS3). IgE could be cross-linked to the Fc epsilon R on the intact cells with either reagent and, in addition, up to 10% of the B cell surface immunoglobulin (sIg; both IgM and IgD) was also found to cross-link to the IgE/Fc epsilon R complex. Analysis of isolated sIg/IgE/Fc epsilon R complexes indicated that about 60% of the Fc epsilon molecules were becoming cross-linked to sIg. Thus, the data suggest that on the intact murine B cell the Fc epsilon R is frequently in close association with sIg. The murine B cell Fc epsilon R was also examined for the presence of receptor-associated proteins that are buried in the membrane. Advantage was taken of the membrane-impermeant nature of DTSSP and BS3. IgE was cross-linked to the Fc epsilon R on intact cells by using the disulfide-cleavable DTSSP and following solubilization with nonionic detergent; BS3 was used to cross-link possible internal membrane components to the Fc epsilon R. In these experiments, the high-affinity Fc epsilon R on rat basophilic leukemia (RBL) cells could be cross-linked to a nonreducible high molecular weight complex of 100 kilodaltons. However, when intact murine B cells were treated with DTSSP, solubilized and treated with BS3 in the same manner as indicated above, no evidence was found for the presence of membrane-buried receptor-associated proteins with the B cell Fc epsilon R. Thus, these data further support the concept that there may be little relationship between the high-affinity mast cell/basophil Fc epsilon R and the low-affinity lymphocyte Fc epsilon R.

The murine lymphocyte receptor for IgE. III. Use of chemical cross-linking reagents to further characterize the B lymphocyte Fc epsilon receptor

Cross-linking reagents were used to further characterize the murine B cell receptor for the Fc portion of IgE (Fc epsilon R) and compare this receptor to the well-characterized high-affinity Fc epsilon R on rat basophilic leukemia (RBL) cells. The disulfide cleavable and noncleavable reagents 3,3'-dithiobis(sulfosuccinimidyl) propionate (DTSSP) and bis(sulfosuccinimidyl) suberate (BS3) were used. With these reagents, efficient cross-linking of the alpha component of the high-affinity RBL Fc epsilon R to the membrane-buried beta and gamma components occurred only if the membrane was solubilized before the cross-linking reaction. In studies with purified murine B cells, IgE could be cross-linked to the Fc epsilon R on intact cells with either DTSSP or BS3. Under the same conditions, up to 10% of the B cell surface immunoglobulin (sIg) (both IgM and IgD) was also found to cross-link to a portion of the IgE/Fc epsilon R complex, suggesting that on the intact murine B cell the Fc epsilon R is frequently in close association with sIg. The B cell Fc epsilon R was also examined for the presence of receptor-associated proteins. Under conditions where the high-affinity RBL Fc epsilon R was substantially cross-linked to the alpha, beta, gamma complex, no evidence was seen for similar cross-linking of the B cell Fc epsilon R. Cross-linking experiments on affinity-purified Fc epsilon R preparations also gave no evidence for receptor-associated proteins with the B cell Fc epsilon R, although evidence for receptor-receptor association was seen. Thus, these data further support the concept that there may be little relationship between the high-affinity mast cell/basophil Fc epsilon R and the low-affinity lymphocyte Fc epsilon R.

The murine lymphocyte receptor for IgE. III. Use of chemical cross-linking reagents to further characterize the B lymphocyte Fc epsilon receptor

Cross-linking reagents were used to further characterize the murine B cell receptor for the Fc portion of IgE (Fc epsilon R) and compare this receptor to the well-characterized high-affinity Fc epsilon R on rat basophilic leukemia (RBL) cells. The disulfide cleavable and noncleavable reagents 3,3'-dithiobis(sulfosuccinimidyl) propionate (DTSSP) and bis(sulfosuccinimidyl) suberate (BS3) were used. With these reagents, efficient cross-linking of the alpha component of the high-affinity RBL Fc epsilon R to the membrane-buried beta and gamma components occurred only if the membrane was solubilized before the cross-linking reaction. In studies with purified murine B cells, IgE could be cross-linked to the Fc epsilon R on intact cells with either DTSSP or BS3. Under the same conditions, up to 10% of the B cell surface immunoglobulin (sIg) (both IgM and IgD) was also found to cross-link to a portion of the IgE/Fc epsilon R complex, suggesting that on the intact murine B cell the Fc epsilon R is frequently in close association with sIg. The B cell Fc epsilon R was also examined for the presence of receptor-associated proteins. Under conditions where the high-affinity RBL Fc epsilon R was substantially cross-linked to the alpha, beta, gamma complex, no evidence was seen for similar cross-linking of the B cell Fc epsilon R. Cross-linking experiments on affinity-purified Fc epsilon R preparations also gave no evidence for receptor-associated proteins with the B cell Fc epsilon R, although evidence for receptor-receptor association was seen. Thus, these data further support the concept that there may be little relationship between the high-affinity mast cell/basophil Fc epsilon R and the low-affinity lymphocyte Fc epsilon R.

The murine lymphocyte receptor for IgE. II. Characterization of the multivalent nature of the B lymphocyte receptor for IgE

The murine B lymphocyte Fc epsilon R is functionally multivalent. Radiolabeled rat IgE, when bound to the B cell Fc epsilon R will co-isolate with the Fc epsilon R on a rat IgE affinity column; examination of the affinity column eluate by SDS-PAGE reveals the component previously identified as the Fc epsilon R as well as E and L chains from IgE. At low levels of Fc epsilon R saturation, up to 30% of the Fc epsilon R bound IgE becomes bound to IgE-Affi-Gel. By using a biotin-avidin system, the coprecipitation of non-haptenated IgE with haptenated IgE was examined and the results suggest (but do not prove) a divalent receptor.

Two-dimensional echocardiographic features of Björk-Shiley aortic prosthetic valve dehiscence

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Pulmonary coin lesions: a ten-year review of 239 cases

The results of a study of 239 resected solitary pulmonary nodules are presented; 66.5% of the resected nodules were malignant, and there were three patients with malignant coin lesions who were under 30 years of age. These findings confirm the generally accepted fact that most solitary pulmonary nodules must be resected if the presence of cancer is to be excluded. Transbronchial biopsy under biplane fluoroscopic guidance through a flexible bronchoscope may provide an effective alternative to early thoracotomy in the future, so that malignant nodules can be diagnosed before operation and patients with benign lesions are spared a thoracotomy.