Cognate interactions between helper T cells and B cells. II. Dissection of cognate help by using a class II-restricted, antigen-specific, IL-2-dependent helper T cell clone

In order to determine the involvement of T-B cell contact vs lymphokine production in mediating B cell cycle entry and progression, Th cell clones "defective" in lymphokine production were cloned. Th-3.1 is one such clone that required IL-2 to produce significant levels of IL-4 and IFN-gamma. Unlike conventional Th clones, Th-3.1 induced B cell proliferation only in the presence of Ag and IL-2. In contrast to the absolute requirement of IL-2 for Th-3.1-induced B cell proliferation, IL-2 was not required for the formation of stable Th-3.1-B cell conjugates or Th-3.1-induced B cell entry into the G1 phase of the cell cycle. In the absence of IL-2 and under conditions that promoted Th-B cell interactions, Th-3.1 induced 10 to 20% of resting B cells to enter G1. B cell entry into the cell cycle was not inhibited by anti-lymphokine mAb or promoted by exogenous lymphokines, suggesting that endogenous lymphokine activity was not required for Th-3.1-induced G0 to G1 transition. The data suggested that the IL-2-independent induction of B cells into G1 by Th-3.1 was a cell contact-dependent event. Direct proof that Th-3.1-B cell contact was necessary for B cell cycle entry was provided by comparative in situ analysis of the RNA synthetic activity and the RNA content of B cells that were in physical contact with Th-3.1 or not in contact with Th-3.1. In situ autoradiography of RNA synthesis illustrated that a high frequency of B cells in contact with Th-3.1 expressed heightened RNA synthetic activity, whereas "bystander" B cells were less frequently induced into cycle. In situ laser cytometry of B cell size and total RNA content showed that B cells in physical contact with Th-3.1 had a higher RNA content and were larger than "bystander" B cells present in the same microcultures. This model system has allowed the dissection of T cell help into IL-2-dependent and IL-2-independent phases. Early cell contact-dependent events and B cell cycle progression into G1 were IL-2 independent, whereas the production of lymphokines (IL-4, IFN-gamma) by Th-3.1 and Th-3.1-induced B cell proliferation was IL-2 dependent.

Cognate interactions between helper T cells and B cells. II. Dissection of cognate help by using a class II-restricted, antigen-specific, IL-2-dependent helper T cell clone

In order to determine the involvement of T-B cell contact vs lymphokine production in mediating B cell cycle entry and progression, Th cell clones "defective" in lymphokine production were cloned. Th-3.1 is one such clone that required IL-2 to produce significant levels of IL-4 and IFN-gamma. Unlike conventional Th clones, Th-3.1 induced B cell proliferation only in the presence of Ag and IL-2. In contrast to the absolute requirement of IL-2 for Th-3.1-induced B cell proliferation, IL-2 was not required for the formation of stable Th-3.1-B cell conjugates or Th-3.1-induced B cell entry into the G1 phase of the cell cycle. In the absence of IL-2 and under conditions that promoted Th-B cell interactions, Th-3.1 induced 10 to 20% of resting B cells to enter G1. B cell entry into the cell cycle was not inhibited by anti-lymphokine mAb or promoted by exogenous lymphokines, suggesting that endogenous lymphokine activity was not required for Th-3.1-induced G0 to G1 transition. The data suggested that the IL-2-independent induction of B cells into G1 by Th-3.1 was a cell contact-dependent event. Direct proof that Th-3.1-B cell contact was necessary for B cell cycle entry was provided by comparative in situ analysis of the RNA synthetic activity and the RNA content of B cells that were in physical contact with Th-3.1 or not in contact with Th-3.1. In situ autoradiography of RNA synthesis illustrated that a high frequency of B cells in contact with Th-3.1 expressed heightened RNA synthetic activity, whereas "bystander" B cells were less frequently induced into cycle. In situ laser cytometry of B cell size and total RNA content showed that B cells in physical contact with Th-3.1 had a higher RNA content and were larger than "bystander" B cells present in the same microcultures. This model system has allowed the dissection of T cell help into IL-2-dependent and IL-2-independent phases. Early cell contact-dependent events and B cell cycle progression into G1 were IL-2 independent, whereas the production of lymphokines (IL-4, IFN-gamma) by Th-3.1 and Th-3.1-induced B cell proliferation was IL-2 dependent.

Role of transcriptional termination in the regulation of mu mRNA expression in B lymphocytes

The synthesis of mRNA for mu-chain of membrane vs secretory IgM in normal resting B lymphocytes is stringently regulated. Very minimal amounts of microseconds mRNA are produced until the cells are stimulated. We have found a strong correlation between the initiation of mu S mRNA production and an alteration in the site of termination of polymerases transcribing the mu-gene. Furthermore, since the abundance of mu S mRNA is dependent on the differentiation stage of the B lymphocyte, we examined subpopulations of cells at various stages of activation and found that along with increased initiation of polymerases at the mu-locus, termination is moved further upstream in more highly differentiated cells. Therefore regulation of mu S mRNA may require factor(s) that induce transcriptional termination and these may be related to the factor(s) that augment transcriptional initiation.

Role of transcriptional termination in the regulation of mu mRNA expression in B lymphocytes

The synthesis of mRNA for mu-chain of membrane vs secretory IgM in normal resting B lymphocytes is stringently regulated. Very minimal amounts of microseconds mRNA are produced until the cells are stimulated. We have found a strong correlation between the initiation of mu S mRNA production and an alteration in the site of termination of polymerases transcribing the mu-gene. Furthermore, since the abundance of mu S mRNA is dependent on the differentiation stage of the B lymphocyte, we examined subpopulations of cells at various stages of activation and found that along with increased initiation of polymerases at the mu-locus, termination is moved further upstream in more highly differentiated cells. Therefore regulation of mu S mRNA may require factor(s) that induce transcriptional termination and these may be related to the factor(s) that augment transcriptional initiation.

Regulation of B lymphocytes by natural killer cells. Role of IFN-gamma

Using a co-culture system of fractionated B cells and highly purified NK cells, we have demonstrated direct interactions between B lymphocytes and NK cells. B cells are able to stimulate the production of IFN-gamma by NK cells. This stimulatory ability is restricted to a subpopulation of large, presumably in vivo activated B lymphocytes. The secreted IFN-gamma in turn inhibits polyclonally induced B cell proliferation. Small resting B cells neither stimulate IFN-gamma production nor are they measurably affected by NK cells.

Regulation of B lymphocytes by natural killer cells. Role of IFN-gamma

Using a co-culture system of fractionated B cells and highly purified NK cells, we have demonstrated direct interactions between B lymphocytes and NK cells. B cells are able to stimulate the production of IFN-gamma by NK cells. This stimulatory ability is restricted to a subpopulation of large, presumably in vivo activated B lymphocytes. The secreted IFN-gamma in turn inhibits polyclonally induced B cell proliferation. Small resting B cells neither stimulate IFN-gamma production nor are they measurably affected by NK cells.

The human immunoglobulin C mu-C delta locus: regulation of mu and delta RNA expression during B cell development

Whether the immunoglobulin (Ig) heavy chain genes C mu and C delta are expressed singly or in combination, their transcripts undergo differentiation-specific alterations in membrane (M) versus secreted (S) forms as well as in abundance. To better understand this regulation, we have cloned cDNAs for human delta m and delta s to establish the 3' end of the C mu-C delta transcription unit. Steady state mRNA levels and transcription rates were then analyzed in normal and transformed human B cells representing different maturation and activation states. The ratio of micron/microsecond RNA and of delta m/delta s RNA correlated with developmental stage, with a higher ratio at earlier stages. Steady state ratios of total mu/delta RNA paralleled ratios of C mu/C delta nascent transcription, suggesting no major posttranscriptional control for differential expression. However, at all developmental stages, transcription termination occurred downstream of the micron exons, suggesting a strong posttranscriptional regulatory component for production of secreted versus membrane forms of mu RNA. The relative abundance of mature delta S RNA was considerably higher in the human than in the mouse, correlating with the increased levels of circulating IgD in the former species. Stimulation of human splenocytes with mitogens did not increase delta RNA; in fact, splenocytes activated with pokeweed mitogen were nearly devoid of delta RNA, and Staphylococcus aureus Cowan I caused only a minor change.

Alternative expression of secreted and membrane forms of immunoglobulin mu-chain is regulated by transcriptional termination in stable plasmacytoma transfectants

During B cell differentiation the mu H chain of IgM is produced initially as a cell surface (m) and later as a secreted (s) form. Production of either the secreted (microseconds) or the membrane (micron) mRNA results from selection of either the promoter proximal (microseconds) or distal (micron) poly(A)/cleavage site. We have transfected lymphoid cell lines of disparate developmental stages with productively rearranged Ig mu-chain constructs to determine the mechanism by which alternative 3' end selection is achieved. Stable transfectants of lymphomas (early stage, microseconds less than or equal to micron) and a plasmacytoma (late stage, microsecond much greater than micron) produce the anticipated levels of microsecond and micron mRNA. Transcription termination between the microsecond and micron poly(A) sites occurs only in the plasmacytoma transfectants, and appears to be the rate-limiting step in the production of the final steady state microsecond/micron mRNA ratio. We propose that as the B cell becomes terminally committed to secretion, the mechanism responsible for the regulation of the steady state microsecond/micron mRNA ratio shifts from exclusively post-transcriptional to predominantly transcriptional termination.

Alternative expression of secreted and membrane forms of immunoglobulin mu-chain is regulated by transcriptional termination in stable plasmacytoma transfectants

During B cell differentiation the mu H chain of IgM is produced initially as a cell surface (m) and later as a secreted (s) form. Production of either the secreted (microseconds) or the membrane (micron) mRNA results from selection of either the promoter proximal (microseconds) or distal (micron) poly(A)/cleavage site. We have transfected lymphoid cell lines of disparate developmental stages with productively rearranged Ig mu-chain constructs to determine the mechanism by which alternative 3' end selection is achieved. Stable transfectants of lymphomas (early stage, microseconds less than or equal to micron) and a plasmacytoma (late stage, microsecond much greater than micron) produce the anticipated levels of microsecond and micron mRNA. Transcription termination between the microsecond and micron poly(A) sites occurs only in the plasmacytoma transfectants, and appears to be the rate-limiting step in the production of the final steady state microsecond/micron mRNA ratio. We propose that as the B cell becomes terminally committed to secretion, the mechanism responsible for the regulation of the steady state microsecond/micron mRNA ratio shifts from exclusively post-transcriptional to predominantly transcriptional termination.

Alpha 1-adrenergic stimulation of cardiac gene transcription in neonatal rat myocardial cells. Effects on myosin light chain-2 gene expression

Previous studies have demonstrated that alpha-adrenergic stimulation of cultured, neonatal rat myocardial cells results in an increase in intracellular volume and protein content of cultured neonatal rat myocardial cells. Utilizing this model of cardiac hypertrophy, we have examined the effects of alpha-adrenergic stimulation on the accumulation of sarcomeres and the expression of a rat cardiac myofibrillar gene, myosin light chain-2 (MLC-2). Following alpha-adrenergic stimulation, cultured myocardial cells displayed a severalfold increase in the number of sarcomeric units, as assessed by electron microscopy, an increase in cellular MLC-2 content, and a 2-3 fold increase in the steady state levels of MLC-2 mRNA. This effect of alpha-adrenergic stimulation was accompanied by a 2-3-fold increase in total transcriptional activity, which was dependent on the concentration and duration of exposure to the agonist, and displayed alpha 1-adrenergic receptor specificity. The transcriptional response was not immediate, with a lag period of at least 1 h, and a maximal effect required continuous occupancy of the receptor. The increase in steady state levels of MLC-2 mRNA is regulated, in part, at the level of transcription of the cardiac MLC-2 gene. These results suggest that alpha 1-adrenergic stimulation may be important in the growth of the neonatal heart through the activation of total transcriptional activity. In addition, increases in the levels of myofibrillar proteins during myocardial cell growth and hypertrophy, may be mediated in part by the stimulation of transcription of myofibrillar genes.

Transcriptional regulation of mu and delta gene expression in bone marrow pre-B and B lymphocytes

Newly formed B cells first express IgM and subsequently display IgD on the cell surface. This is an ontologically, as well as developmentally, regulated process because IgD is virtually absent on neonatal splenic B cells. In the present studies we have examined, by means of nascent RNA chain labeling, the relative levels of mu to delta gene transcription in bone marrow B cells, pre-B cells, and earlier progenitors of B cells. Pre-B cells were obtained from Whitlock-type long term cultures of bone marrow cells from normal and C.B17 scid mice. Both populations were found to transcribe the delta gene at very low but detectable levels. A similarly low level of delta transcription was found to occur in surface IgM-positive cells from both cultured and freshly isolated bone marrow B cells. In all populations analyzed, termination of the majority of polymerases occurred within a discrete 1-kb region located between the microM and C delta I exons. Analysis of steady state RNA indicated that long term cultured bone marrow cells from normal mice produced both 2.7-kb normal sized microM mRNA as well as 2.9-kb aberrantly spliced I mu-mRNA, whereas those from C.B17 scid mice contained only aberrant sized mu-mRNA. In contrast to these results, our previous findings with spleen cells obtained from both neonatal and adult animals showed that delta gene transcription occurs at a relatively high level. Therefore, it is possible that activation of regulatory signals that allow polymerases to progress beyond the termination site 3' of the microM exons may occur when newly formed B cells migrate from the bone marrow to the splenic environment.

Transcriptional regulation of mu and delta gene expression in bone marrow pre-B and B lymphocytes

Newly formed B cells first express IgM and subsequently display IgD on the cell surface. This is an ontologically, as well as developmentally, regulated process because IgD is virtually absent on neonatal splenic B cells. In the present studies we have examined, by means of nascent RNA chain labeling, the relative levels of mu to delta gene transcription in bone marrow B cells, pre-B cells, and earlier progenitors of B cells. Pre-B cells were obtained from Whitlock-type long term cultures of bone marrow cells from normal and C.B17 scid mice. Both populations were found to transcribe the delta gene at very low but detectable levels. A similarly low level of delta transcription was found to occur in surface IgM-positive cells from both cultured and freshly isolated bone marrow B cells. In all populations analyzed, termination of the majority of polymerases occurred within a discrete 1-kb region located between the microM and C delta I exons. Analysis of steady state RNA indicated that long term cultured bone marrow cells from normal mice produced both 2.7-kb normal sized microM mRNA as well as 2.9-kb aberrantly spliced I mu-mRNA, whereas those from C.B17 scid mice contained only aberrant sized mu-mRNA. In contrast to these results, our previous findings with spleen cells obtained from both neonatal and adult animals showed that delta gene transcription occurs at a relatively high level. Therefore, it is possible that activation of regulatory signals that allow polymerases to progress beyond the termination site 3' of the microM exons may occur when newly formed B cells migrate from the bone marrow to the splenic environment.

Transient expression of pentameric IgM on the surface of NZB B cells

In contrast to normal B lymphocytes, splenic B cells from autoimmune NZB mice express on their surface greater amounts of IgM than IgD. We have found that the predominant mu chain species present on these cells is derived from pentameric secretory IgM which can be radioiodinated during transient association with the cell membrane. If the contribution from 19S IgM is discounted, then the surface IgM:IgD ratio of NZB mice is only moderately higher than that of B cells from normal strains.

Relationships between histology, monoclonal antibody reactivity, and prognosis in breast cancer

Infiltrating ductal carcinoma of the breast is histologically heterogeneous and may be subdivided into three main types (A, B, and C) which correlate with the likelihood of long-term survival. Examples of each type were tested against three monoclonal antibodies (H59, H71, and H72) prepared against the breast cancer cell line ZR-75-1. The reaction patterns of type B tumors were significantly different from those of types A and C with antibodies H59 and H71, but not with H72. Thus, the reactivity to these monoclonal antibodies, and presumably the antigen composition of the tumor cells, correlates with the histologic appearances and probability of long-term survival.

The expression and regulation of c-myb transcription in B6/lpr Lyt-2-, L3T4-T lymphocytes

Mice homozygous for the lpr gene spontaneously develop massive lymphoproliferation and an associated lupus-like autoimmune disease. In addition, the total lymphoid organs from these mice express high levels of mRNA for the c-myb proto-oncogene. Since enhanced c-myb mRNA is normally observed in immature thymic lymphocytes but not normal peripheral T cells, this may be indicative of the abnormal maturation state of lpr T lymphocytes. To determine whether the abnormal Lyt-2-, L3T4- (double negative) T lymphocytes in lpr mice express high c-myb, we purified this population by complement-mediated lysis with anti-L3T4 and Lyt-2 antibody from B6/lpr lymph nodes. We found that increased c-myb mRNA is expressed by this double-negative subset. To assess whether the high level of c-myb correlated with the aberrant undifferentiated state of these cells, we examined the effects of T cell differentiation inducers, phorbol ester and calcium ionophore, on c-myb expression. We found that c-myb levels were depressed after phorbol ester and calcium ionophore treatment. Concomitantly, transcriptional activation of the interleukin 2 receptor gene and progression of these cells through the cell cycle were observed. Thus, in B6/lpr double-negative T cells, the regulation of c-myb, interleukin 2 receptor, and cell proliferation may be interrelated. A combination of Northern hybridization and nuclear run-on transcription assays revealed two levels at which c-myb can be regulated in the double-negative T cell subset. The gene is transcriptionally regulated in untreated cells, but on induction with phorbol ester and calcium ionophore, the gene is negatively regulated via post-transcriptional mechanisms.

The expression and regulation of c-myb transcription in B6/lpr Lyt-2-, L3T4-T lymphocytes

Mice homozygous for the lpr gene spontaneously develop massive lymphoproliferation and an associated lupus-like autoimmune disease. In addition, the total lymphoid organs from these mice express high levels of mRNA for the c-myb proto-oncogene. Since enhanced c-myb mRNA is normally observed in immature thymic lymphocytes but not normal peripheral T cells, this may be indicative of the abnormal maturation state of lpr T lymphocytes. To determine whether the abnormal Lyt-2-, L3T4- (double negative) T lymphocytes in lpr mice express high c-myb, we purified this population by complement-mediated lysis with anti-L3T4 and Lyt-2 antibody from B6/lpr lymph nodes. We found that increased c-myb mRNA is expressed by this double-negative subset. To assess whether the high level of c-myb correlated with the aberrant undifferentiated state of these cells, we examined the effects of T cell differentiation inducers, phorbol ester and calcium ionophore, on c-myb expression. We found that c-myb levels were depressed after phorbol ester and calcium ionophore treatment. Concomitantly, transcriptional activation of the interleukin 2 receptor gene and progression of these cells through the cell cycle were observed. Thus, in B6/lpr double-negative T cells, the regulation of c-myb, interleukin 2 receptor, and cell proliferation may be interrelated. A combination of Northern hybridization and nuclear run-on transcription assays revealed two levels at which c-myb can be regulated in the double-negative T cell subset. The gene is transcriptionally regulated in untreated cells, but on induction with phorbol ester and calcium ionophore, the gene is negatively regulated via post-transcriptional mechanisms.

Effect of (D-Trp6, Pro9-NEt)-GnRH on the function and ultrastructure of pituitary and testis in male rats

Groups of ten adult male Wistar rats were treated chronically with GnRH agonist for different durations. The responses of pituitary and testis to GnRH agonist were evaluated by serum and testicular testosterone, serum and pituitary LH, and testicular LH receptors. Testicular testosterone and LH receptors were decreased very significantly under our experimental regimen, irrespective of the duration of the treatment Serum testosterone levels were reduced after 10 and 15 injections, but only rats receiving 10 injections showed a significant increase in serum LH levels and decrease of pituitary LH content. The type II gonadotropes of the pars distalis of pituitary were increased in number but showed a higher degree of dilated smooth endoplasmic reticulum with few secretory granules. Many large lipid droplets appeared in the cytoplasms of the Leydig cells. Degenerative changes were observed in most seminiferous tubules following GnRH agonist treatment. Obvious abnormal acrosome and nuclear caps of some spermatids were also observed. The functional changes caused by GnRH agonist coincided with their ultrastructural appearance.

Regulation of immunoglobulin D synthesis in murine neonatal B lymphocytes

We analyzed the regulatory basis for the lower expression of immunoglobulin D (IgD) in lymphocytes from neonatal mice of various ages. The results indicate that the relative transcriptional rate of RNA for delta chains is similar to adult levels even in cells which have not started to express IgD. These results suggest that very early after the initiation of mu gene transcription, a defined fraction of polymerases is programmed to progress through the termination site to the delta exons regardless of the developmental stage of the cell. Similar results were obtained from adult CBA/N mice whose spleens contain a large fraction of cells expressing low levels of IgD. On the other hand, the relative steady state level of mRNA in neonatal lymphocytes is approximately half of that in adults, suggesting that there may be differences in the processing or stability of the nascent transcript. In addition, measurements of the in vivo translation rate show that an inefficient delta polypeptide chain processing machinery in neonatal lymphocytes is also an important factor contributing to the reduced expression of IgD.

Activation of the gamma 1 gene by lipopolysaccharide and T cell-derived lymphokines containing a B cell differentiation factor for IgG1 (BCDF gamma)

By using both pulse labeling of nascent RNA chains and lactoperoxidase-catalyzed cell surface radioiodination, we examined both the de novo synthesis of mRNA for gamma-chains and the expression of membrane IgG (mIgG) on cells which had been stimulated with LPS plus a T cell supernatant (SN) containing a B cell differentiation factor for IgG1 (BCDF gamma). Our results show that neither nascent mRNA for gamma 1 chains nor mIgG1 can be detected in B lymphocytes until they have been stimulated by both LPS and BCDF gamma-containing T cell SN, and suggest that cell surface expression and secretion of IgG1 are coordinately controlled.

Activation of the gamma 1 gene by lipopolysaccharide and T cell-derived lymphokines containing a B cell differentiation factor for IgG1 (BCDF gamma)

By using both pulse labeling of nascent RNA chains and lactoperoxidase-catalyzed cell surface radioiodination, we examined both the de novo synthesis of mRNA for gamma-chains and the expression of membrane IgG (mIgG) on cells which had been stimulated with LPS plus a T cell supernatant (SN) containing a B cell differentiation factor for IgG1 (BCDF gamma). Our results show that neither nascent mRNA for gamma 1 chains nor mIgG1 can be detected in B lymphocytes until they have been stimulated by both LPS and BCDF gamma-containing T cell SN, and suggest that cell surface expression and secretion of IgG1 are coordinately controlled.

Regulation of expression of immunoglobulins M and D in murine B cells

Immunoglobulins M (IgM) and D (IgD) are expressed in a coordinantly regulated and differentiation-dependent fashion on the surface of B lymphocytes. We have studied the role of DNA configuration of their linked constant region genes C mu and C delta, as well as their transcription and posttranscriptional processing, in the regulation of these changes. After rearrangement of variable region segments, IgD can be singularly expressed in plasmacytoma cells by a DNA deletion of the C mu gene that is mediated by illegitimate recombination. However, IgM and IgD are usually expressed jointly without further DNA rearrangement downstream of VDJ. In pre-B cells, C delta apparently is not transcribed before light-chain expression. However, in early neonates (2 days old), C delta is transcribed at approximately one-third the level of C mu even though IgD is not detectable on the cell surface. This same ratio of transcription is preserved in older neonates (12 days old), which express only modest quantities of IgD, and in mature resting B cells, which express far higher densities of cell surface IgD than IgM. On activation by mitogens, transcription of C mu is preferentially enhanced, but it is surprising that C delta transcription remains at the baseline level even though cytoplasmic delta mRNA is virtually undetectable. The apparent discrepancy in transcription and ultimate expression can be explained by further modifications of both the RNA and polypeptide chains. Collectively, our data show that the differential expression of IgM and IgD is regulated by complex mechanisms at several levels.

Effect of gossypol on the potential difference of rat seminiferous tubules

The p.d. of the rat seminiferous tubules was 4.75 +/- 1.39 mV (lumen negative) at 35 degrees C and varied linearly with temperatures from 26 to 40 degrees C. A depolarization of the seminiferous tubules was found in the rats administered with gossypol at the dosage of 30 mg/kg body weight for 3 weeks, the p.d. lowered to 3.63 +/- 0.79 mV at 35 degrees C and was independent of the changes of seminiferous tubules temperature. In the 5-week-gossypol-treatment group, the tracer penetrated not only the myoid cell layer, but also went beyond the tight junction complexes between Sertoli cells. The lanthanum appeared in the cleft surrounding spermatogonia. In the 8-week-gossypol-treatment group, the lanthanum was found in the adluminal compartment. It indicates that gossypol can cause a dysfunction of the Sertoli cells and blood-testis barrier and disturb a good physiological environment for the developing spermatocytes.

Relationship of monoclonal antibody binding to estrogen and progesterone receptor content in breast cancer

Three monoclonal antibodies--H59, H71, and H72--which react with human breast cancers have been developed using the estrogen-dependent human breast cancer cell line, ZR-75-1, as the immunogen. H59 bound only to estrogen receptor-positive, estrogen-regulated breast cancer cells in culture, whereas H71 and H72 bound breast cancer cells irrespective of the estrogen receptor content. All three antibodies have minimal cross-reactivity with non-breast tissue culture cell lines. The three antigens appear to be glycoproteins located on the cell surface. H59 and H72 antigens bound preferentially to the apical surface of duct cells and may be secreted; H71 antigen demonstrated no evidence of an apical orientation or secretion. The binding of the antibodies to fixed cryosections from 152 breast cancer and 111 benign breast disease specimens has been evaluated using a radioimmunoassay. Eighty-five % of breast cancer and almost 100% of benign disease specimens were bound by at least one antibody. H59 bound 39%, H71 bound 51%, and H72 bound 65% of cancer specimens. Estrogen receptor and progesterone receptor analyses were obtained on 141 specimens. H59 bound almost exclusively to tumor specimens which contained estrogen and/or progesterone receptor, but not to all receptor-positive tumors. Therefore, the H59 antigen appeared to be present on a subset of estrogen receptor-positive tumors. Considering that it bound only to estrogen-regulated cells in culture, the antigen may be estrogen regulated, and its presence may predict a response to hormone therapy. H71 and H72 recognized cell surface differentiation antigens but bound tumor specimens regardless of the receptor content. These antibodies may be useful as independent variables for predicting response to therapy and prognosis of patients with breast cancer.

Transcriptional regulation of the mu-delta heavy chain locus in normal murine B lymphocytes

The heavy chain genes for IgM (C mu) and IgD (C delta) are expressed differentially during B cell maturation and activation. We have determined the role that transcription plays in the regulation of these changes by using the method of in vitro nascent RNA chain elongation. In neonatal cells that express much lower densities of IgD than IgM on their surface, transcription of C delta is observed at half the level of C mu. This 3:1 transcriptional ratio of mu to delta is preserved in mature resting cells, which express higher densities of IgD on the surface than IgM. When activated by the mitogen, lipopolysaccharide (LPS), transcription of C mu is preferentially enhanced. However, C delta transcription is not shut off even though the expression of IgD in the stimulated cells is greatly decreased. In all three differentiative stages, polymerase unloading occurs in the vicinity of a large inverted repeat sequence, 5' to C delta and 3' to the mu membrane exons. This suggests that the developmental selection of secreted vs. membrane-bound carboxyl-terminal exons is controlled by RNA cleavage. The data presented here, together with our previous analysis of mRNA and protein synthesis, show that the differential expression of IgM and IgD in normal B lymphocytes is regulated at the transcriptional, translational, and posttranslation levels.

Regulation of IgM and IgD synthesis in B lymphocytes. II. Translational and post-translational events

Studies investigating the relative rates of biosynthesis of mu- and delta-polypeptide chains in normal resting B lymphocytes have shown that the translation rate of mu m is about sevenfold higher than that of delta m, thus reflecting the relative abundance of mRNA encoding these two chains. The turnover rate of cell surface IgM is faster, however, than that of cell surface IgD, resulting in higher expression of cell surface IgD relative to IgM under steady state conditions. LPS stimulation of B lymphocytes induces the complete cessation of synthesis of the delta-chain, thus accounting for the gradual disappearance of IgD from the cell surface of activated cells.

Regulation of IgM and IgD synthesis in B lymphocytes. II. Translational and post-translational events

Studies investigating the relative rates of biosynthesis of mu- and delta-polypeptide chains in normal resting B lymphocytes have shown that the translation rate of mu m is about sevenfold higher than that of delta m, thus reflecting the relative abundance of mRNA encoding these two chains. The turnover rate of cell surface IgM is faster, however, than that of cell surface IgD, resulting in higher expression of cell surface IgD relative to IgM under steady state conditions. LPS stimulation of B lymphocytes induces the complete cessation of synthesis of the delta-chain, thus accounting for the gradual disappearance of IgD from the cell surface of activated cells.

Regulation of IgM and IgD synthesis in B lymphocytes. I. Changes in biosynthesis of mRNA for mu- and delta-chains

Although IgD is expressed on the surface of resting B cells at a higher density than IgM, we determined that both the steady-state level and the biosynthetic rate of mu m-mRNA is higher than that of delta m-mRNA, suggesting that translational or post-translational processing of the Ig heavy chains may modulate the expression of cell surface Ig. After B cell activation by LPS, delta m-mRNA decreases drastically, accounting for the observed decrease in expression of IgD. Concomitantly, a dramatic increase in the level of mu s- and gamma s-mRNA corresponds to the observed increase in secretion of these Ig isotypes in LPS-stimulated cells.

Regulation of IgM and IgD synthesis in B lymphocytes. I. Changes in biosynthesis of mRNA for mu- and delta-chains

Although IgD is expressed on the surface of resting B cells at a higher density than IgM, we determined that both the steady-state level and the biosynthetic rate of mu m-mRNA is higher than that of delta m-mRNA, suggesting that translational or post-translational processing of the Ig heavy chains may modulate the expression of cell surface Ig. After B cell activation by LPS, delta m-mRNA decreases drastically, accounting for the observed decrease in expression of IgD. Concomitantly, a dramatic increase in the level of mu s- and gamma s-mRNA corresponds to the observed increase in secretion of these Ig isotypes in LPS-stimulated cells.

Lymphokine-induced IgM secretion by clones of neoplastic B cells

The induction of antibody secretion by B cells requires T-cell-derived factors1-5. Such factors have been described1,2,6-12 but the precise relationship among these various factors is not clear, and it has been difficult to demonstrate that these factors act directly on the B cell and do not exert their effect via T cells or macrophages. In this report we describe the direct induction of IgM synthesis and secretion in cloned lines of long-term tissue culture adapted neoplastic B cells (BCL1) by T-cell supernatants from phorbol-12-myristate 13-acetate (PMA)-induced EL-4 cells or concanavalin A (Con A)-induced 7.1.1a cells5,9. We have termed this activity BCDFmu (B-cell differentiation factor for IgM). The supernatants containing BCDFmu induce activated and neoplastic B cells to secrete IgM5 and the factor responsible is distinct from BCGF13, interleukin-2 (IL-2)5, the classical T-cell replacing factor (TRF) described by Schimpl and Wecker5, and immune interferon (IFN gamma)5.

Structural studies of cell surface and secreted IgG in LPS-stimulated murine B cells

We have characterized the cell surface IgG of LPS-stimulated B lymphocytes by surface iodination and specific immunoprecipitation. IgG3 was found to be the predominant IgG subclass expressed on the B cell surface after 5 days of stimulation with LPS. In contrast, IgG2b, IgG3, and IgG1 subclasses are all secreted. Cell surface IgG exhibits detergent binding characteristics not shown by secreted IgG and the gamma chains of the three subclasses of surface IgG examined have the apparent mol. wt of 64 Kd, some 9,000 larger than the H chains of secreted IgG.

Effect of lipopolysaccharide stimulation on the transcription and translation of messenger RNA for cell surface immunoglobulin M

Analysis of mu-specific mRNA in the B cell tumor line, BCL1, shows that the cells contain predominantly mRNA for mu chain of membrane-bound immunoglobulin M (IgM) (2.7 kb, mu m mRNA). Stimulation of the cells to Ig secretion by lipopolysaccharide (LPS) results in a 6-12 fold increase in amount of mRNA for the mu chain of secreted IgM (2.4 kb mu s mRNA). The increase in mu s mRNA is accompanied by a 3-4-fold increase in mu m mRNA. The rate of mu chain synthesis of membrane IgM in LPS-stimulated cells is, however, reduced by at least twofold, suggesting that both transcriptional and translational regulatory events are involved in the induction of B lymphocytes to secretion.

Characterization of a monoclonal antibody reactive with a subset of human breast tumors

Fusion of spleen cells, from mice immunized against the human hormone-dependent breast cancer cell line ZR-75-1, with murine myeloma cells resulted in the establishment of a hybridoma cell line, HY59-H10 (H59). The purified monoclonal IgM produced by the hybridoma reacts with the most differentiated human breast tumor cell lines but not with cells derived from normal breast secretions or with numerous other malignant cell lines. Of 106 biopsy specimens examined, H59 bound to 54% of malignant breast specimens, to 83% of fibroadenomas, and to 82% of specimens containing fibrocystic disease.

A peptide difference between the mu-chains from cell-associated and secreted IgM of the BCL1 tumor

The murine B cell tumor, BCL1, bears monomeric IgM lambda on its surface. After stimulation in vitro with LPS, the cells secrete pentameric IgM lambda. Comparison of mu-chains from radiolabeled intracellular, surface, and secreted IgM indicates that mu-chains from the three sites have different apparent m.w. Since the observed differences are analogous to those reported for normal murine lymphoid cells, the BCL1 cells were used for determining the structural basis for the differences in m.w. of mu-chains from the above sites. Comparative peptide analysis was performed on mu-chains from cell associated and secreted IgM. Approximately 25 peptides were identified after digestion with chymotrypsin and trypsin and analysis of peptides by cation exchange chromatography. All peptides co-eluted with the exception of a single extra peptide derived from the Fc portion of the secreted IgM. The same peptide was observed in a similar analysis using mu-chains from IgM secreted by normal splenocytes.

A peptide difference between the mu-chains from cell-associated and secreted IgM of the BCL1 tumor

The murine B cell tumor, BCL1, bears monomeric IgM lambda on its surface. After stimulation in vitro with LPS, the cells secrete pentameric IgM lambda. Comparison of mu-chains from radiolabeled intracellular, surface, and secreted IgM indicates that mu-chains from the three sites have different apparent m.w. Since the observed differences are analogous to those reported for normal murine lymphoid cells, the BCL1 cells were used for determining the structural basis for the differences in m.w. of mu-chains from the above sites. Comparative peptide analysis was performed on mu-chains from cell associated and secreted IgM. Approximately 25 peptides were identified after digestion with chymotrypsin and trypsin and analysis of peptides by cation exchange chromatography. All peptides co-eluted with the exception of a single extra peptide derived from the Fc portion of the secreted IgM. The same peptide was observed in a similar analysis using mu-chains from IgM secreted by normal splenocytes.

The kinetics and mechanisms of the gas phase pyrolyses of exo-2-norbornyl chloride and cyclopentyl chloride

The gas phase pyrolyses of exo-2-norbornyl chloride and cyclopentyl chloride were studied in the temperature range 570–670 K. The results obtained show that these compounds behave as typical secondary halides insofar as the kinetics of their hydrogen chloride elimination reactions are concerned. Labelling experiments showed that in the formation of both norbornene and cyclopentene, a cis-1,2 elimination with a deuterium isotope effect of ∼3 was involved. Nortricyclene also was produced from exo-2-norbornyl chloride, via a trans 1,3 elimination; this process is analogous to a fragmentation of the ionized molecule. No gas phase Wagner–Meerwein rearrangement was involved in the formation of either norbornene or nortricyclene.

Characterization of the spontaneous murine B cell leukemia (BCL1). III. Evidence for monoclonality by using an anti-idiotype antibody

We have raised an anti-idiotypic antibody against the cell surface IgM of the murine BCL1 tumor cells. This antiserum reacts exclusively with the IgM expressed on the tumor cells and detects a unique population of cells in the spleen and blood of the tumor-bearing mice. When these cells are stimulated in vitro with LPS, they secrete an IgM bearing the same idiotype as the cell surface Ig. These results are discussed in terms of a model for the immunotherapy of a chronic lymphocytic leukemia-like syndrome in mice.

Characterization of the Spontaneous Murine B Cell Leukemia (BCL1)

We have raised an anti-idiotypic antibody against the cell surface IgM of the murine BCL1 tumor cells. This antiserum reacts exclusively with the IgM expressed on the tumor cells and detects a unique population of cells in the spleen and blood of the tumor-bearing mice. When these cells are stimulated in vitro with LPS, they secrete an IgM bearing the same idiotype as the cell surface Ig. These results are discussed in terms of a model for the immunotherapy of a chronic lymphocytic leukemia-like syndrome in mice.

A dichotomy between the expression of IgD on B cells and its requirement for triggering such cells with two T-independent antigens

The majority of adult B lymphocytes in the mouse bear two immunoglobulin isotypes, IgM and IgD (mu(+)delta(+) cells) (1). A small population of IgM-bearing cells lacks, or expresses very low levels of IgD (mu- predominant [mup] cells) (1). These cells are believed to constitute a less mature subset of B cells analogous to neonatal B cells (2). Based on the time during ontogeny when responses to T-independent (TI) and T-dependent (TD) antigens appear (3, 4) and the ability to block in vitro responses with anti- mu or anti-delta (5, 6, D. Mosier, personal communication), it has been suggested that the precursors of two TI-1 responses, trinitrophenyl (TNP)- Brucella (TNP-BA) and TNP-lipopolysaccharide (TNP-LPS) are mup cells (5, 6), whereas the precursor for a TD response, TNP-sheep erythrocytes (TNP-SRBC), bears both IgM and IgD (6). However, the possibility cannot be excluded that IgD is present on some or all of the TI precursors, but that it is not obligatory for triggering. In the present experiments we have examined the phenotypes of TI and TD precursors by treating cells with C' and either anti-mu or anti-delta before stimulation with antigen. Our results suggest that the majority of B cells that respond to TNP-BA, TNP-LPS, and TNP-SRBC bear IgD, even though in the case of the two TI antigens, IgD is not required for triggering.

Cell surface immunoglobulin XXI. appearance of IgD on murine lymphocytes during differentiation

The differentiation of Ig-bearing lymphocytes in adult mice was studied by monitoring the appearance of IgD relative to IgM on the surface of splenocytes obtained from lethally irradiated animals reconstituted for various periods of time with adult bone marrow cells, neonatal splenocytes, or Ig- adult splenocytes. It was found that IgM appears before IgD on differentiating lymphocytes. Furthermore, the rate of appearance of IgD during differentiation of adult cells is similar to that observed with neonatal cells.

Cell surface immunoglobulin. XX. Antibody responsiveness of subpopulations of B lymphocytes bearing different isotypes

Murine spleen cells were depleted of specific B-cell subpopulations bearing different immunoglobulin isotypes by means of complement-mediated cytolysis after treatment with antisera specific for micron- and gamma-chains. The functional effect of this depletion was measured by assaying both the primary and secondary plaque-forming cell responses of the residual cells after transfer to carrier-primed lethally irradiated hosts. The results suggest that cells bearing IgM are the progenitors of plaque-forming cells in the primary response and cells bearing IgG are the major progenitors of IgG plaque-forming cells in the secondary response. The quantity of IgM on progenitors of secondary IgM plaque-forming cells decreases markedly as the interval between primary immunization and antigenic challenge increases. Long-term memory cells for the secondary IgM response bear small amounts of both IgM and IgG.

Partial characterization of nervous system-specific cell surface antigen(s) NS-2

Partial biochemical characterization of several neural tissue specific antigens isolated from a murine glioblastoma cell line was accomplished by means of radioiodination of intact cells followed by immunoprecipitation of the cell lysate with a rabbit serum specific for neural tissue antigens. Polyacrylamide gel electrophoresis of the immunoprecipitate in sodium dodecyl sulfate resolved the labeled antigens into several major components: two proteins (or glycoproteins) having apparent m.w.'s of 84,000 and 120,000 and lipid associated components which may be heterogeneous. The protein and lipid associated components apparently possess independent antigenicity because after chloroformmethanol extraction the protein components can be immunoprecipitated from the aqueous phase and the lipid associated component can be immunoprecipitated from the organic phase. Despite their independent antigenicity it is not known whether the components may be noncovalently associated on the cell surface. Although some of these antigens can be isolated from brain or glioma cells (a related tumor), non can be demonstrated in lymphoid tissues or C1300 neuroblastoma cells using identical methods. Therefore, these studies confirm our previous findings concerning the specificity of the anti-NS-2 antiserum by using cytotoxicity tests.

Stability of ribosomal and transfer ribonucleic acid in Escherichia coli B/r after treatment with ethylenedinitrilotetraacetic acid and rifampicin

A short treatment with ethylenedinitrilotetraacetic acid to permeabilize bacteria for various antibiotics or treatment with the ribonucleic acid (RNA) synthesis inhibitor rifampin causes a slow degradation of 50S and 30S ribosomal particles and of the corresponding 23S and 16S ribosomal RNA species (about 25 percent in 1 h). The effects are additive such that the decay is about 50 percent/h if rifampin is employed after permeabilization by ethylenedinitrilotetraacetic acid. The 5S ribosomal RNA and transfer RNA are essentially stable under these conditions.