Normal recombination substrate VH to DJH rearrangements in pre-B cell lines from scid mice.

To further analyze the VDJ recombination defect in lymphoid pre-B cells from mice with severe combined immune deficiency (scid mice), we have assayed the ability of Abelson murine leukemia virus (A-MuLV) transformed pre-B cells from scid mice to rearrange a recombination substrate in which inverted VH to DJH joins activate a selectable (gpt) gene. In unselected populations, substrate rearrangements occurred frequently, but were aberrant and probably analogous to the aberrant rearrangements observed at endogenous scid Ig gene loci. In contrast, populations of scid pre-B lines selected for gpt activity within the substrate contained mostly "normal" VH to DJH joins within the introduced substrate. These findings demonstrate that scid pre-B cells can make normal joins at low efficiency and are discussed with respect to the potential mechanism of the scid defect and the occurrence of Igs in leaky scid mice.

Non-antigen signals for B-cell growth and differentiation to antibody secretion.

Recently, significant progress had been made in understanding the T-B lymphocyte interactions that control humoral immunity. This review highlights experiments that demonstrate a central role for interactions between T-cell-B-cell-activating molecule (CD40 ligand) expressed on T cells and CD40 on B cells in B-cell activation and immunoglobulin isotype switching, both in vitro and in vivo.

Association of simian virus 40 T antigen with the nuclear matrix of infected and transformed monkey cells.

The subnuclear distribution of simian virus 40 large T antigen within nuclei of transformed Cos and C6 monkey cells was examined. Cos cells express wild-type T antigen but lack viral sequences required for DNA replication, whereas C6 cells contain a functional viral origin but express a replication-defective mutant T antigen which is unable to bind specifically to viral DNA. Discrete subpopulations of T antigen were isolated from the soluble nucleoplasm, chromatin, and nuclear matrix of both cell lines. Although only a small quantity (2 to 12%) of the total nuclear T antigen from Cos cells was associated with the nuclear matrix, a high proportion (25 to 50%) of C6 T antigen was bound to this structure. Results obtained from lytically infected monkey cells showed that early in infection, before viral replication was initiated, a higher proportion (22%) of T antigen was found associated with the nuclear matrix compared with amounts found associated with this structure later in infection (5 to 8%). These results suggest that an increased association of T antigen with this structure is not correlated with viral replication. T antigen isolated from the C6 nuclear matrix was more highly phosphorylated than was soluble C6 T antigen and was capable of binding to the host p53 protein. C6 DNA contains three mutations: two corresponding to N-terminal changes at amino acid positions 30 and 51 and a third located internally at amino acid position 153. By analysis of the subnuclear distribution of T antigen from rat cells transformed by C6 submutant T antigens, it was determined that one or both of the mutations at the NH2 terminus are responsible for the increased quantity of C6 T antigen associated with the nuclear matrix. These results suggest that neither a functional viral DNA replication origin nor the origin binding property of T antigen is required for association of this protein with the nuclear matrix.

DNA-binding properties of simian virus 40 T-antigen mutants defective in viral DNA replication.

Three simian virus 40 (SV40)-transformed monkey cell lines, C2, C6, and C11, producing T-antigen variants that are unable to initiate viral DNA replication, were analyzed with respect to their affinity for regulatory sequences at the viral origin of replication. C2 and C11 T antigens both bound specifically to sequences at sites 1 and 2 at the viral origin region, whereas C6 T antigen showed no specific affinity for any viral DNA sequences under all conditions tested. Viral DNA sequences encoding the C6 T antigen have recently been cloned out of C6 cells and used to transform an established rat cell line. T antigen from several cloned C6-SV40-transformed rat lines failed to bind specifically to the origin. C6 DNA contains three mutations: two located close to the amino terminus of T antigen at amino acid positions 30 and 51 and a third located internally at amino acid position 153. Two recombinant SV40 DNA mutants were prepared containing either the amino-terminal mutations at positions 30 and 51 (C6-1) or the internally located mutation at position 153 (C6-2) and used to transform Rat 2 cells. Whereas T antigen from C6-2-transformed cells lacked any specific affinity for these sequences. Therefore, the single mutation at amino acid position 153 (Asn leads to Thr) is sufficient to abolish the origin-binding property of T antigen. A T antigen-specific monoclonal antibody, PAb 100, which had been previously shown to immunoprecipitate an immunologically distinct origin-binding subclass of T antigen, recognized wild-type or C6-1 antigens, but failed to react with C6 or C6-2 T antigens. These results indicate that viral replication function comprises properties of T antigen that exist in addition to its ability to bind specifically to the SV40 regulatory sequences. Furthermore, it is concluded from these data that specific viral origin binding is not a necessary feature of the transforming function of T antigen.

The effect of the scid mutation on mechanism and control of immunoglobulin heavy and light chain gene rearrangement.

Most Abelson murine leukemia virus (A-MuLV)-transformed cell lines derived from scid (severe combined immune deficient) mice actively rearrange their endogenous immunoglobulin (Ig) heavy (H), but not light (L) chain variable region genes. Such cell lines express germline VH segments and other RNA transcripts that are characteristically produced by early precursor (pre)-B lymphocytes, but do not express high levels of transcripts from the germline kappa (k) constant region (C kappa) locus. However, we have derived scid A-MuLV transformants that express germline C kappa transcripts and attempt kappa gene assembly. In one case kappa gene expression and rearrangement occurred in the absence of mu H chain expression, and in another was not induced efficiently by introduction of a mu-expression vector. Although the vast majority of scid H and L chain coding sequence joins are grossly aberrant, scid A-MuLV transformants can form normal coding joints at a very low frequency. In contrast, these cells form generally normal signal sequence joins at an approximately normal efficiency. Thus, these findings mechanistically distinguish coding and signal join formation. Subcloning analyses suggest that scid A-MuLV transformants that do not attempt chromosomal coding sequence joining may have a relative survival advantage, and therefore that these events may often result in unrepaired chromosomal breakage and cell death.

Isolation of cDNAs encoding T-BAM, a surface glycoprotein on CD4+ T cells mediating contact-dependent helper function for B cells: identity with the CD40-ligand.

"T-cell B-cell Activating Molecule" (T-BAM) is an activation-induced surface protein on CD4+ T cells that mediates a contact-dependent signal for B cell differentiation and immunoglobulin (Ig) secretion. The T-BAM protein on a helper clone of Jurkat (D1.1) was affinity purified using the anti-T-BAM mAb, 5c8. The NH2-terminal amino acid sequence of purified T-BAM was determined and found to be highly homologous to the predicted NH2-terminal sequence of a T cell ligand to the B cell CD40 molecule (CD40-L). From a D1.1 cDNA library, a clone was isolated that encodes CD40-L by sequence and drives expression of T-BAM protein on transfected cells, demonstrating that the T-BAM and CD40-L genes and proteins are identical. Moreover, transfection of T-BAM was shown to confer to non-lymphoid cells, the ability to induce B cells to upregulate the expression of surface CD23 molecules. In previous studies we showed that T-BAM was expressed predominantly on activated CD4+ and on few if any CD8+ cells. Although the current work confirms that T-BAM is largely restricted to activated CD4+ T cells, we now provide definitive evidence that T-BAM can be expressed by a small population of CD8+ T cells after activation. Importantly, a subset of CD8+ T cells do not express T-BAM after activation and this T-BAM- phenotype is maintained on certain CD8+ T cell clones. Taken together, these data unify the biology and structure of T-BAM and CD40-L and this synthesis has implications for understanding the T cell regulation of the humoral immune response.

Smoking cessation, clonidine, and vulnerability to nicotine among dependent smokers.

OBJECTIVE: This study examines the efficacy of clonidine in smoking cessation and the influence of gender, history of major depression, and measures of nicotine dependence. METHODS: The study was designed as a 10-week double-blind randomized comparison stratified for gender and major depression. Three hundred subjects who smoked cigarettes heavily were enrolled in the study. Abstinence from smoking was evaluated by self-report and verified by serum cotinine levels. RESULTS: Gender, major depression recurrent type, and measures of nicotine addiction were risk factors for treatment failure. There was no clonidine effect in men, but there was a modest effect in women (odds ratio, 2.01; 95% confidence interval, 1.00 to 4.10) that was most pronounced (odds ratio, 8.5; 95% confidence interval, 1.67 to 43.62) among women with the highest risks. CONCLUSION: Measures of addiction and major depression predict treatment failure. Together they are stronger predictors of outcome than drug. Clonidine is a limited aid in cessation, and drug effects come primarily from women at high risk for treatment failure. An increased risk for psychiatric complications after smoking cessation was apparent among smokers with histories of major depression, particularly bipolar disease.

Major depression following smoking cessation.

OBJECTIVE: The authors examined the incidence and predictors of major depression following successful smoking cessation treatment, with special attention to the influence of past major depression. METHOD: Three-month follow-up data were obtained from 126 subjects who successfully completed a 10-week smoking cessation program. RESULTS: The 3-month incidence of new major depression following treatment for nicotine dependence was 2%, 17%, and 30% among subjects with histories of no major depression, single major depression, and recurrent major depression, respectively. A history of major depression and persistent withdrawal symptoms independently predicted posttreatment major depression. CONCLUSIONS: Continued patient care beyond the 2-4-week period associated with the nicotine withdrawal syndrome is indicated when abstinence is attempted by smokers with prior major depression.

Effect of history of alcoholism or major depression on smoking cessation.

The authors examined the influence of a history of alcoholism or major depression on smoking cessation for 220 subjects. The success rate of recovering alcoholics was comparable to that of nonalcoholics, comorbidity of alcoholism and major depression exerted a detrimental effect, and smoking cessation did not precipitate an alcoholic relapse.

Mood, major depression, and fluoxetine response in cigarette smokers.

OBJECTIVE: Two smoking cessation studies provided venues to 1) look for differences in affective symptoms between cigarette smokers with and without a history of major depression or other psychiatric diagnoses who were not currently depressed and 2) evaluate the efficacy of fluoxetine in ameliorating affective symptoms in smokers with a history of major depression but not currently depressed. METHOD: Part I: Three hundred sixty-eight smokers who enrolled in a smoking cessation treatment study completed baseline self-rating scales. The relationship between the scale scores and a history of major depression and other psychiatric diagnoses was examined. Part II: Thirty-nine smokers with a history of major depression were enrolled in a randomized, double-blind study that examined the utility of fluoxetine as an aid to smoking cessation. Self-rated scales were compared at baseline and after 3 weeks of medication treatment before the attempt to quit. RESULTS: A history of major depression had significant main effects across all scale scores; subjects with such a history rated themselves as more symptomatic. The effects of other psychiatric diagnoses were neither as pervasive nor as robust. There were no differences in baseline scores between the fluoxetine- and placebo-treated groups and no change within the placebo group after 3 weeks. There was significant improvement from baseline in several subscale scores for the group treated with fluoxetine. However, comparison of the score changes for the placebo and fluoxetine groups did not show a statistically significant difference, which limited the ability to conclude that active treatment was better than placebo. CONCLUSIONS: Subjects with a history of major depression, but without current affective illness, reported themselves to be more symptomatic than those without such-a history. Furthermore, in a group of smokers with a history of major depression, affective symptoms, without concurrent syndromal illness, may be ameliorated by treatment with fluoxetine.

CD40:CD40L interactions in X-linked and non-X-linked hyper-IgM syndromes.

Hyper-IgM (HIM) syndrome is a rare immunodeficiency characterized by low or absent IgG, IgA, and IgE with normal or elevated levels of IgM. This disorder can be acquired or familial with either X-linked or autosomal patterns of inheritance. The X-linked form of the disease is a consequence of mutations in the CD40 ligand (CD40L) gene that encodes a protein expressed primarily on activated CD4+ T cells. The cognate interaction between CD40L on T cells and CD40 on antigen-stimulated B cells, macrophage, and dendritic cells is critical for the development of a comprehensive immune response. The non-X-linked form of HIM syndrome is heterogeneous and appears in some cases to be a consequence of mutations in the AlD gene which encodes a B cell specific protein required for class switch recombination, somatic mutation, and germinal center formation. However, mutations in other unidentified genes are clearly the basis of the disease in a subset of patients. In this article, we review the essential features of the X-linked and non-X-linked forms of HIM syndrome and discuss the critical role the CD40:CD40L receptor-ligand pair plays in the pathogenesis of these immune deficiencies.

Gender differences in autoantibodies to oxidative DNA base damage in cigarette smokers.

Oxidative DNA damage and antibodies to that damage have been implicated in lung, breast, and colorectal cancer. In this observational validation study, the relationship between anti-5-hydroxymethyl-2'-deoxyuridine (HMdU) autoantibody (aAb) and plasma micronutrients was assessed in 140 heavy smokers by ELISA. Anti-HMdU aAbs were 50% higher in women after adjustment for cigarettes/day (CPD; P = 0.002), although men smoked more and had higher plasma cotinine levels. The women reported taking more vitamin C (P < 0.005) and had higher plasma levels of alpha-carotene and beta-carotene (P < 0.001) and cryptoxanthin (P < 0.01) than men. Neither CPD nor cotinine was associated with aAb titers. Anti-HMdU aAbs were associated inversely with alpha-tocopherol (P = 0.10), retinol (P = 0.06), and age (P = 0.04) in women but not in men. In contrast to the men, women 50 years of age (P = 0.05). Given the same duration of exposure, women had higher anti-HMdU aAbs and also reached peak levels at a lower cumulative smoking exposure (30 years) compared with male smokers (40 years). Subjects smoked an average of 28.9 +/- 0.81 CPD and initiated smoking at 17.2 +/- 0.33 (SE) years of age. Therefore, smokers who reported smoking for 30 years were typically <50 years old. Women

Decline of DNA damage and other biomarkers in peripheral blood following smoking cessation.

Serial samples from 40 heavy smokers ( > or = pack/day for > or = 1 year) enrolled in a smoking cessation program were assayed for cotinine, polycyclic aromatic hydrocarbon (PAH)-DNA, 4-aminobiphenyl-hemoglobin (4-ABP-Hb) adducts, and glycophorin A (GPA) mutations. Blood samples were taken while subjects were smoking, and 10 weeks and 8 and 14 months after quitting. Cotinine was used to assess compliance with the cessation protocol. A significant reduction in mean PAH-DNA and 4-ABP-Hb adducts was observed after cessation in all persons who were cotinine-verified quitters ( < or = 25 ng/ml) for > or = 8 months (P < 0.05). Neither the GPA N/phi nor the GPA N/N mutation Vf was significantly reduced after smoking cessation, but results are limited by the small number (n = 18) of heterozygous individuals studied. The substantial reduction (50-75%) in PAH-DNA and 4-ABP-Hb adduct levels after quitting indicates these carcinogen adducts are reflective of smoking. Passive exposure to smoke at home was significantly associated with PAH-DNA adducts in active smokers and in ex-smokers 10 weeks after quitting (P < 0.01). The estimated half-life of the PAH-DNA adducts in leukocytes is 9-13 weeks by inspection of the mean biomarker levels from baseline and 10 weeks sample and 23 (95% confidence interval, 10-36 weeks) using a linear regression model that adjusted for background.(ABSTRACT TRUNCATED AT 250 WORDS)

Advances in non-nicotine pharmacotherapy for smoking cessation.

Progress in understanding the pharmacological nature of tobacco addiction, along with the modest success rates achieved by the nicotine replacement therapies, has provided the major impetus for the development of non-nicotine drugs as smoking cessation aids. This article reviews evidence from controlled trials of several non-nicotine medications for the treatment of nicotine dependence. Clonidine was the first non-nicotine medication to show efficacy for smoking cessation in multiple studies, but its effect was found to be limited at best. Positive results across several trials have been consistently demonstrated for amfebutamone (bupropion). Encouraging results have also been observed for nortriptyline and moclobemide. Studies of combined treatments using non-nicotine medications (amfebutamone, mecamylamine, oral dextrose) with nicotine replacement therapy suggest increased efficacy relative to treatments using one or the other treatment strategy alone. Thus, available evidence indicates that non-nicotine drug treatments offer a promising panoply of therapeutic strategies for the addicted smoker.

Depression after smoking cessation: case reports.

BACKGROUND: Cigarette smokers with a history of major depression are at risk for developing depressive mood when they attempt cessation. Whether cessation can also provoke more severe depressions, however, has not been well documented. METHOD: Six case reports of severe depressive episodes after smoking cessation are described. RESULTS: Four cases occurred among smokers with a history of major depression but who were not depressed at the time of cessation. Two cases involved smokers with no previous history of major depression. Variability in both the timing and the outcome of the postcessation depressions was observed. CONCLUSION: The risk that depressive states may emerge or be exacerbated after smoking cessation, particularly in patients with a history of major depression, must be kept in mind in the treatment of nicotine dependence.

Cigarette smoking and major depression.

The authors review recent literature that has demonstrated an association between cigarette smoking behavior and major depression. Persons with major depression are more likely to smoke and to have difficulty when they try to stop. When they manage to succeed in stopping, such persons are at increased risk of experiencing mild to severe states of depression, including full blown major depression. The period of vulnerability to a new depressive episode appears to vary from a few weeks to several months after cessation. This knowledge suggests a relationship between smoking and depression that is complex, pernicious, and potentially life-long. It is recommended that cessation treatments incorporate screening procedures that will identify those patients with a propensity to depression and monitor the emergence of postcessation depression, particularly in those with a history of depression.

Naltrexone effects on short-term and long-term smoking cessation.

OBJECTIVES: This study examined the efficacy of naltrexone, a long-acting opiate antagonist, as a smoking cessation aid in a double-blind placebo-controlled randomized trial. It was hypothesized that naltrexone would result in higher quit rates at the end of treatment and six months later. METHODS: Subjects were 68 smokers aged 18 to 65 who smoked at least 20 cigarettes daily and wished to stop smoking. They took naltrexone or placebo daily for four weeks and were seen weekly for individual smoking cessation therapy. RESULTS: A statistical trend towards a higher overall cessation rate (cotinine < 15 ng/mL) at end-of-treatment was observed among subjects treated with naltrexone than placebo (46.7% vs. 26.3%, respectively, odds ratio = 2.5, p < .10); however, this difference was attenuated at six months (27% vs. 15%, respectively, odds ratio = 1.9, p = ns). Stratified analysis indicated the usefulness of naltrexone primarily for female smokers and those with a history of major depression. These effects remained six months later. CONCLUSION: These results provide, at best, mild promise for naltrexone as a smoking cessation drug and provide another instance of a differential response to nicotine dependence treatment according to gender and depression history.

Tobacco cessation among patients with depression.

This article summarizes the research evidence on the association between smoking and depression. Across multiple studies and clinical and population-based samples, it has been demonstrated that, compared with nondepressed individuals, persons with depression are more likely to be smokers, to be dependent smokers, to have difficulty stopping smoking, and to experience more severe withdrawal symptoms. Further, they may be at risk of experiencing severe depression once they have stopped smoking. Based on the author's experience with this population of smokers, recommendations for assessing smokers' vulnerability to depression, their level of nicotine dependence, and psychological and pharmacological aids for smokers are offered.