Therapeutic misunderstandings in modern research

Clinical trials play a crucial role in generating evidence about healthcare interventions and improving outcomes for current and future patients. For individual trial participants, however, there are inevitably trade-offs involved in clinical trial participation, given that trials have traditionally been designed to benefit future patient populations rather than to offer personalised care. Failure to understand the distinction between research and clinical care and the likelihood of benefit from participation in clinical trials has been termed the 'therapeutic misconception'. The evolution of the clinical trials landscape, including greater integration of clinical trials into healthcare and development of novel trial methodologies, may reinforce the significance of the therapeutic misconception and other forms of misunderstanding while at the same time (paradoxically) challenging its salience. Using cancer clinical trials as an exemplar, we describe how methodological changes in early- and late-phase clinical trial designs, as well as changes in the design and delivery of healthcare, impact upon the therapeutic misconception. We suggest that this provides an impetus to re-examine the ethics of clinical research, particularly in relation to trial access, participant selection, communication and consent, and role delineation.

Ferritin levels throughout childhood and metabolic syndrome in adolescent stage

BACKGROUND AND AIM

Increased ferritin levels have been widely associated with cardiovascular risk in adults. Whether ferritin levels and their changes during childhood are related to metabolic syndrome (MetS) at adolescence is unknown. We aimed to evaluate these associations using levels of ferritin at 5, 10 and 16 years and their linear increases and patterns of sustained increased levels across childhood.

METHODS AND RESULTS

There were four samples evaluated according to non-missing values for study variables at each stage (5 years: 562; 10 years: 381; and 16 years: 567 children; non-missing values at any stage: 379). MetS risk was evaluated as a continuous Z score. Patterns of sustained increased ferritin (highest tertile) and slope of the change of ferritin per year across the follow-up were calculated. Ferritin levels in the highest versus lowest tertile at five and 16 years were significantly positively associated with MetS risk Z score at adolescence in boys and these associations were unaffected by adjustment for covariates. Having high, compared to low/moderate ferritin level at 2 or more time periods between 5 and 16 years was related to higher Mets Z-score in boys only [e.g. 5-10 years adjusted-beta (95 %CI):0.26 (0.05-0.48),P < 0.05]. In girls, ferritin Z score at 10 and 16 years was positively and independently associated with HOMA-IR Z score. In girls, the slope of ferritin per year in the highest tertile was positively associated with MetS risk Z-score [adjusted-beta (95 %CI):0.21 (0.05-0.38),P < 0.05].

CONCLUSIONS

Ferritin levels throughout childhood are positively related to cardiometabolic risk in adolescence, with associations varying by sex.

TACTIC: a multicentre, open-label, single-arm phase II trial of panitumumab, cisplatin, and gemcitabine in biliary tract cancer

PURPOSE

The phase II TACTIC trial prospectively selected patients with KRAS wild-type advanced biliary tract cancer for first-line treatment with panitumumab and combination chemotherapy.

METHODS

Of 78 patients screened, 85 % had KRAS wild-type tumours and 48 were enrolled. Participants received cisplatin 25 mg/m(2) and gemcitabine 1000 mg/m(2) on day 1 and day 8 of each 21-day cycle and panitumumab 9 mg/kg on day 1 of each cycle. Treatment was continued until disease progression, unacceptable toxicity, or request to discontinue. The primary endpoint was the clinical benefit rate (CBR) at 12 weeks (complete response, partial response, or stable disease). CBR of 70 % was considered to be of clinical interest. Secondary outcomes were progression-free survival, time to treatment failure, overall survival, CA19.9 response and safety.

RESULTS

Thirty-four patients had a clinical benefit at 12 weeks, an actuarial rate of 80 % (95 % CI 65-89 %). 46 % had a complete or partial response. Median progression-free survival was 8.0 months (95 % CI 5.1-9.9) and median overall survival 11.9 months (95 % CI 7.4-15.8). Infection accounted for 27 % of the grade 3 or 4 toxicity, with rash (13 %), fatigue (13 %), and hypomagnesemia (10 %) among the more common grade 3 or 4 non-haematological toxicities.

CONCLUSION

A marker-driven approach to patient selection was feasible in advanced biliary tract cancer in an Australian population. The combination of panitumumab, gemcitabine, and cisplatin in KRAS wild-type cancers was generally well tolerated and showed promising clinical efficacy. Further exploration of anti-EGFR therapy in a more selected population is warranted.

GWAS for executive function and processing speed suggests involvement of the CADM2 gene

To identify common variants contributing to normal variation in two specific domains of cognitive functioning, we conducted a genome-wide association study (GWAS) of executive functioning and information processing speed in non-demented older adults from the CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology) consortium. Neuropsychological testing was available for 5429-32,070 subjects of European ancestry aged 45 years or older, free of dementia and clinical stroke at the time of cognitive testing from 20 cohorts in the discovery phase. We analyzed performance on the Trail Making Test parts A and B, the Letter Digit Substitution Test (LDST), the Digit Symbol Substitution Task (DSST), semantic and phonemic fluency tests, and the Stroop Color and Word Test. Replication was sought in 1311-21860 subjects from 20 independent cohorts. A significant association was observed in the discovery cohorts for the single-nucleotide polymorphism (SNP) rs17518584 (discovery P-value=3.12 × 10(-8)) and in the joint discovery and replication meta-analysis (P-value=3.28 × 10(-9) after adjustment for age, gender and education) in an intron of the gene cell adhesion molecule 2 (CADM2) for performance on the LDST/DSST. Rs17518584 is located about 170 kb upstream of the transcription start site of the major transcript for the CADM2 gene, but is within an intron of a variant transcript that includes an alternative first exon. The variant is associated with expression of CADM2 in the cingulate cortex (P-value=4 × 10(-4)). The protein encoded by CADM2 is involved in glutamate signaling (P-value=7.22 × 10(-15)), gamma-aminobutyric acid (GABA) transport (P-value=1.36 × 10(-11)) and neuron cell-cell adhesion (P-value=1.48 × 10(-13)). Our findings suggest that genetic variation in the CADM2 gene is associated with individual differences in information processing speed.

Hepatic steatosis and non-alcoholic fatty liver disease are not associated with decline in renal function in people with Type 2 diabetes

AIMS

We aimed to determine whether the presence of hepatic steatosis and/or non-alcoholic fatty liver disease was associated with decline in renal function or onset of microalbuminuria in a cohort of people with Type 2 diabetes, including those managed in both primary and secondary care.

METHODS

Nine hundred and thirty-three patients from the Edinburgh Type 2 Diabetes Study, a cohort of Scottish men and women aged 60-74 years with Type 2 diabetes, underwent assessment for hepatic steatosis by liver ultrasonography 1 year after recruitment. Non-alcoholic fatty liver disease was defined as the presence of steatosis following exclusion of secondary causes of liver disease. Patients were followed for 4 years and decline in renal function was assessed by the change in estimated glomerular filtration rate over time.

RESULTS

Of the 933 subjects, 530 had hepatic steatosis and, of those with hepatic steatosis, 388 had non-alcoholic fatty liver disease. Neither hepatic steatosis nor non-alcoholic fatty liver disease were significantly associated with rate of decline in renal function, with the mean rate of decline in estimated glomerular filtration rate being -1.55 ml min(-1) 1.73 m(-2) per year for participants with hepatic steatosis compared with -1.84 ml min(-1) 1.73 m(-2) for those without steatosis (P = 0.19). Similar results were obtained when the analysis was restricted to participants with and without non-alcoholic fatty liver disease (-1.44 vs. -1.64 ml min(-1) 1.73 m(-2) per year, respectively; P = 0.44). Additionally, neither hepatic steatosis nor non-alcoholic fatty liver disease were associated with the onset or regression of albuminuria during follow-up (all P ≥ 0.05).

CONCLUSIONS

The presence of hepatic steatosis/non-alcoholic fatty liver disease was not associated with decline in renal function during a 4-year follow-up in our cohort of older people with Type 2 diabetes.

Contralateral risk-reducing mastectomy in BRCA1/2 mutation carriers and other high-risk women in the Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer (kConFab)

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Background: Contralateral risk-reducing mastectomy (CRRM) reduces contralateral breast cancer (BC) risk by up to 97%. Few studies have examined the prevalence and predictors of CRRM in BC patients at high familial risk of a second primary BC. Methods: Participants were women with unilateral BC and a strong family history of the disease, including BRCA1 and BRCA2 mutation carriers. Data were collected by interview, self-administered questionnaire, and review of pathology and surgical reports. Associations between having CRRM and potential predictors were assessed using multivariate logistic regression. Results: Of 1018 study participants (median follow-up 5.5 years), 154 (15%) underwent CRRM. The median time from initial BC to CRRM was 1 year. More likely to undergo CRRM were women who were younger at the time of their BC diagnosis (odds ratio [OR] = 0.94 per year of age, p < 0.001), those diagnosed more recently (OR = 1.16 per calendar year, p < 0.001), those who underwent mastectomy rather than breast conservation as their initial definitive BC treatment (OR = 5.2, p < 0.001) and those who underwent risk-reducing salpingo-oophorectomy (OR = 3.4, p < 0.001). BRCA1/2 mutation status and tumor characteristics were not independently associated with CRRM uptake. A contralateral BC event occurred in 177 (20.5%) of the 864 women who did not have CRRM, compared with one chest wall event (0.6%) in the 154 women post-CRRM. Conclusions: Younger women with more recently diagnosed BC treated with mastectomy were most likely to elect CRRM. BRCA1/2 mutation status and the competing risk of BC recurrence and death did not appear to influence decision making.

No significant financial relationships to disclose.

Patients’ experiences and reported barriers to screening colonoscopy: A systematic review

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Background: Colonoscopy is a component of most colorectal screening programs, as a primary test or as follow-up to an abnormal FOB test. Little is known about why some patients do not comply with colonoscopy after being referred. Methods: A search strategy using three themes of screening, colonoscopy, and patient acceptance was developed and used in MEDLINE, EMBASE and PSYCHinfo (1996–2008). Retrieved citations were assessed for eligibility by two reviewers using prespecified criteria. A qualitative synthesis was conducted. Results: From an initial 3,174 studies, 264 were identified as potentially eligible for review. After full text assessment, 64 studies met eligibility criteria and were included in the final analysis. Six studies examined the experience of a primary colonoscopy by eliciting patients’ views soon after they had the test. Fifty-six studies addressed patient-reported concerns and barriers to an anticipated primary colonoscopy. Most patients perceived the laxative bowel preparation to be the most burdensome part and the greatest barrier to colonoscopy. Other reported difficulties included anxiety and anticipation of pain. Feelings of embarrassment and vulnerability occurred, particularly in women, and also acted as barriers to adherence. Inadequate knowledge about screening was common and was identified as an obstacle to the uptake of screening colonoscopy as was fear of finding cancer. Physician endorsement, having a family history, knowing someone with cancer, and perceived accuracy of the test were incentives to having a colonoscopy. The most common reported practical barriers were inconvenience, transportation, scheduling, and cost. Only two studies focused on colonoscopy as a secondary procedure in the screening context. Similar procedural, personal, and practical concerns were reported by patients in this setting. Conclusions: Bowel preparation, lack of awareness of the importance of screening, and feelings of vulnerability in women are all significant barriers to colonoscopy in the screening context. These obstacles need to be addressed, and further research undertaken on barriers to second line colonoscopy.

No significant financial relationships to disclose.

Cancer risk management practices of non-carriers within BRCA1/2 mutation positive families in the Kathleen Cunningham Consortium for Research into Familial Breast Cancer (kConFab)

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Background: This study prospectively evaluated risk management practices of true BRCA1/2 negative women. Methods: A questionnaire was mailed to 471 non-carriers from mutation positive families 3 years after their enrolment in the kConFab breast cancer (BC) family cohort study. Women who had received their mutation result had pre-test counselling and result disclosure in one of 16 Family Cancer Clinics nationwide. Undertaking mammography more often than 2 yearly (Australian population guidelines), clinical breast examination (CBE) more often than yearly, breast self-examination (BSE) more often than monthly and any trans-vaginal ultrasound (TVU) or CA-125 was considered over screening. Linear logistic regression was used to identify factors (age, marital status, education, parity, ethnicity, place of residence, time since disclosure of result, family history) associated with over screening. Results: 347 women responded (74%); 260 were excluded from this analysis (self-reported not knowing their mutation status, 207; uninformative screening data due to proximity of result disclosure to questionnaire administration, 47; developed cancer, 3; pregnancy, 3), leaving 87 subjects. Mean follow up was 4.4 years. Proportions over-screening were; mammography 53%, CBE 10%, BSE 11%, TVU 10% and CA125 10%. No measured factor was associated with over-utilization of BC screening. Women with > one relative with OC were significantly more likely to over-utilize TVU (OR 8.1, CI 1.6–42 P=0.01) and CA125 (OR 19.6, CI 3.1–121 P=0.001) compared to women with ≤ one relative with OC. One woman underwent bilateral mastectomy and 1 bilateral oophorectomy; none used chemoprevention. Conclusions: A major benefit of learning one′s negative mutation status is that the intensity of risk management practices can be reduced to that appropriate for the general population. However, non-carriers with a strong family history of OC tend to inappropriately use OC screening. The reasons are unclear but need elucidation given the potential for harm. The reasons for over-utilization of mammography in 53% also warrant further study.

No significant financial relationships to disclose.

Does the autoantibody immunodominant region on thyroid peroxidase include amino acid residues 742-771?

Identification of the thyroid peroxidase (TPO) amino acid residues that comprise the autoantibody immunodominant region is an important goal that has proven difficult because of the conformational nature of the epitopes involved. Recent data suggest that the immunodominant region has been located. Thus, by autoantibody recognition of tryptic fragments of native TPO, as well as of conformational portions of TPO expressed as cell-free translates, the autoantibody immunodominant region appears to include amino acid residues 742-771, near the C terminus of the ectodomain. To evaluate this deduction, we expressed as cell-free translates the full TPO ectodomain, as well as TPO truncated after residues 741 and 771. The epitopic integrity of these molecules was first confirmed by immunoprecipitation by patient sera containing TPO autoantibodies. However, autoantibody recognition could involve a minority of TPO autoantibodies with the individual sera, not fulfilling the strict criteria for immunodominance. In order to obtain definitive data, we performed immunoprecipitations on these TPO variants with four recombinant human monoclonal autoantibodies that define the immunodominant region. All four monoclonal autoantibodies immunoprecipitated TPO 1-741 to the same extent as they did TPO 1-771 and the full TPO ectodomain, indicating that the immunodominant region comprises (at least in large part) amino acid residues upstream of residue 741.

Role of MHC class I expression and CD8(+) T cells in the evolution of iodine-induced thyroiditis in NOD-H2(h4) and NOD mice

Dietary iodine has long been known to influence the development of human autoimmune thyroid disease. In nonobese diabetic (NOD) and NOD-H2(h4) mice elevated dietary iodine has been shown to induce autoimmune thyroid disease. Immune responses to thyroid antigens can be detected in these mouse strains, including T cell responses in the NOD-H2(h4) mouse to thyroid peroxidase. Cell transfer studies and antibody depletion experiments reveal a requirement for both CD4(+) T cells and CD8(+) T cells in the development of thyroid autoimmunity. Histological analyses of the thyroids show that following 1 week of iodine administration MHC class I expression is elevated on thyroid follicular cells and CD4(+) and CD8(+) T cells have begun to infiltrate the gland. Although MHC class II expression on thyroid epithelial cells was also elevated, the tempo of expression was slower and the extent of expression was far less than that for MHC class I. Depletion of CD8(+) T cells at early stages of disease induction inhibited not only thyroid infiltration and autoantibody production but also reduced the levels of MHC expression in the thyroid, suggesting that cytokine production by infiltrating lymphocytes was responsible for the increased MHC expression.

Ultrasmall superparamagnetic iron oxide to enhance MRA of the renal and coronary arteries: studies in human patients

OBJECTIVE

Our goal was to determine the feasibility of using an intravascular MR contrast agent to improve 3D MRA.

MATERIALS AND METHODS

Three-dimensional TOF MRA was performed in nine patients both prior to and following the administration of an ultrasmall particle superparamagnetic iron oxide contrast agent (AMI 227). The lengths of both renal arteries were measured from the maximum intensity projection (MIP) images as well as the individual partitions. Seven of these patients also were studied by a 3D coronary artery MRA sequence. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements of the right coronary artery were determined both prior to and following the administration of AMI 227. Statistical analysis of both renal artery lengths and right coronary SNR and CNR was performed using a one tailed paired t test comparing pre- and postcontrast images.

RESULTS

The renal artery lengths significantly increased (right and artery: 30%, p = 0.001; left renal artery: 25%, p < 0.008) when measured from the individual axial slice partitions. No significant increase in length was observed on the MIP images following contrast. In the right coronary artery, the SNR increased by an average of 80% (p = 0.008) and CNR increased by an average of 109% (p = 0.007). Increased background signal and superimposed venous structures reduced the measurable lengths of the renal arteries from the MIP images.

CONCLUSION

These studies support the hypothesis that 3D MRA in the body will benefit from the use of intravascular contrast agents. Nevertheless, conventional MIP processing is unable to reveal the full advantage of the contrast improvement.

Dextran-coated superparamagnetic iron oxide, an MR contrast agent for assessing lymph nodes in the head and neck

PURPOSE

To investigate dextran-coated superparamagnetic iron oxide particles (BMS 180549) as an MR contrast agent for assessing lymph nodes.

METHODS

Five different doses ranging from 0.3 to 1.7 mg Fe/kg were evaluated in five healthy human male subjects as part of a phase 1 clinical study. T1-, T2-, and proton density-weighted spin-echo images as well as multiplanar gradient-echo and spoiled gradient-echo images were acquired before and 1 hour, 4 hours, and 24 hours after contrast administration. Image analysis was performed with visually selected regions of interest. Signal intensities were measured for neck lymph nodes and the adjacent muscle. Enhancement effects were evaluated as a function of dose, imaging time after contrast administration, and MR pulse sequence.

RESULTS

The iron oxide particles were phagocytized by macrophages within the normal functioning lymph nodes, resulting in a dramatic decrease in signal intensity because of magnetic susceptibility effects. T2*-weighted gradient echo and T2-weighted spin echo showed significant decrease in the signal intensity of normal lymph nodes at 24 hours after contrast injection at a dose of 1.7 mg Fe/kg. No significant changes in lymph node signal intensity on T1-weighted spin-echo images were noted at any dose or imaging time point.

CONCLUSIONS

This preliminary clinical evaluation demonstrates intravenous delivery of an iron-based contrast agent, resulting in negative enhancement of normal lymph nodes.

Human organ-specific autoimmune disease. Molecular cloning and expression of an autoantibody gene repertoire for a major autoantigen reveals an antigenic immunodominant region and restricted immunoglobulin gene usage in the target organ

The most common organ-specific autoimmune disease in humans involves the thyroid. Autoantibodies against thyroid peroxidase (TPO) are present in the sera of virtually all patients with active disease. We report the molecular cloning of the genes for 30 high-affinity, IgG-class human autoantibodies to TPO from thyroid-infiltrating B cells. Analysis of the putative germline genes used for the TPO human autoantibodies suggests the use of only five different H and L chain combinations involving four H chains and three L chains. In addition, the same combination of H and L chains was found in multiple patients. The F(ab) proteins expressed by these genes define two major, closely associated domains (A and B) in an immunodominant region on TPO. These A and B domains contain the binding sites of approximately 80% of IgG-class TPO autoantibodies in the sera of patients with autoimmune thyroid disease. The present information permits analysis, not previously possible, of the relationship between autoantibody H and L chain genes and the antigenic domains on an autoantigen. Our data, obtained using target organ-derived autoantibodies, indicate that there is restriction in H and L chain usage in relation to the interaction with specific antigenic domains in human, organ-specific autoimmune disease.

Autosomal dominant inheritance of autoantibodies to thyroid peroxidase and thyroglobulin--studies in families not selected for autoimmune thyroid disease

Recently the tendency to produce autoantibodies to thyroid peroxidase (TPO Ab) and thyroglobulin (Tg Ab) was shown to be inherited as an autosomal dominant characteristic in women but not in men. Because of potential bias in this study which was carried out in families with autoimmune thyroid disease (AITD), the inheritance of thyroid autoantibodies has been evaluated in 49 families unselected for autoimmune thyroid disease. Among these families (24 with facioscapulohumeral disease, 10 with Friedreich's ataxia, and 15 with schizophrenia) the prevalences of TPO Ab and Tg Ab were 27.8% and 26.7%, respectively, in women and 9.2% and 11.7%, respectively, in men. In 40 families where one or more individual had TPO Ab and/or Tg Ab, segregation analysis showed that the tendency to make antibodies was consistent with a Mendelian dominant trait in women but not in men. In young women, however, the prevalence of both TPO Ab and Tg Ab increased with age, rising from 14% and 10%, respectively, at age 15-24 to 35% and 40% at age 35-44. As this is inconsistent with a simple dominant hypothesis, a further segregation analysis by age was carried out in the families unselected for thyroid disease together with 16 pedigrees with AITD previously studied and two additional large AITD families. The results of the combined analysis provided strong support for the hypothesis of dominant inheritance but also showed significant reduction in gene expression among women aged 15-24 yr.

Autosomal dominant transmission of autoantibodies to thyroglobulin and thyroid peroxidase

The inheritance of autoantibodies to thyroglobulin and thyroid peroxidase (thyroid microsomal antigen) has been reevaluated with newly developed ultrasensitive assays that depend on the direct interaction between antibody and radiolabeled antigen. In a study of 16 families with autoimmune thyroid disease, autoantibodies to thyroid peroxidase (TPO) were found to be inherited as a dominant Mendelian trait in females with reduced penetrance in males. Similar results were obtained with thyroglobulin (Tg) autoantibodies. Genetic linkage analysis of the loci for TPO and Tg autoantibodies with 28 polymorphic serological markers (including HLA and Gm allotypes) was carried out in 9 families. LOD scores for some serological markers (such as Gm) were uninformative, but linkage with other markers, notably the HLA antigens -A, B, -DR, -DQ, and BF on chromosome 6, could be excluded. Further studies using a comprehensive panel of gene probes to analyze DNA from families with autoimmune thyroid disease should permit the localization of the gene cluster responsible for regulating the ability to produce autoantibodies to TPO and Tg in man.

Atypical T lymphoproliferative disorder demonstrating in vitro suppressor and helper characteristics

A patient initially diagnosed on surface marker status as having T cell chronic lymphatic leukaemia (T-CLL) was found to have arthropathy and recurrent pulmonary infarction associated with a high anti-DNA antibody titre. The T cell from this patient, on assessment in an in vitro pokeweed mitogen driven B cell system, demonstrated suppressor and helper characteristics but lacked antibody dependent cellular cytotoxicity (ADCC) activity and natural killer (NK) activity. Using peripheral blood mononuclear cells (PBM) from patients with Hashimoto's thyroiditis and normals, it was shown that the patient's T cells suppressed both IgG and thyroid autoantibody production. Irradiation of the patient's PBM inhibited the suppressor effect and a residual helper effect remained. The patient was treated with systemic steroids for exacerbations of arthropathy which caused a fall in lymphocyte count. After 36 months the DNA binding activity spontaneously improved and the lymphocytosis disappeared. It is indicated that T-cell proliferations demonstrating functional activity must be assessed within the context of any underlying non-haematological clinical and laboratory findings.

Chemical carcinogen induction of DNA-repair synthesis in human peripheral blood monocytes

Fresh ex vivo cultures of normal human peripheral blood monocytes, which are nonreplicative and known to possess cytochrome P-450 associated mixed-function oxidase activity, were used to assay DNA-excision repair manifested as augmented [3H]thymidine (dThd) incorporation following treatment in culture with diverse mutagenic carcinogens. Untreated monocyte cultures established from pools of 3-6 normal donors incorporated a low level of cytoplasmic [3H]dThd throughout a majority of the cells during an 18-h incubation. This background incorporation into whole cells was 80-90% inhibited by hydroxyurea (HU) at concentrations greater than 5 mM. Dose-related increases in the cumulative 18-h [3H]dThd incorporation in monocytes were observed following treatment with UV, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), methyl methanesulfonate (MMS), mitomycin C (MMC), N-acetoxy-acetylaminofluorene (NA-AAF), aflatoxin B1 (AFB1), benzo[a]pyrene (BaP), and dimethylnitrosamine (DMN). The presence of HU during chemical treatment and throughout this 18 h of incubation with [3H]dThd did not influence the dose-response curves obtained with UV, MMS, NA-AAF and BaP but it increased the input dose of MNNG, MMC, DMN and AFB1 required to give peak repair incorporation. When HU was added to cultures following MNNG damage no interference with repair response was observed. HU apparently influences the extent of DNA damage by direct reactivity with these chemicals or their endogenously generated metabolites rather than inhibiting DNA-repair processes. These results provide evidence that monocytes are enzymatically proficient in base and nucleotide excision pathways and have endogenous capacity to metabolize BaP, AFB1 and DMN to DNA-damaging metabolites. As such, the monocyte is a potentially useful human cell type for detecting genotoxic chemicals and studying individuality in chemical-biological interactions.

Thyroglobulin and microsomal autoantibody production by cultures of Hashimoto peripheral blood lymphocytes

Peripheral blood lymphocytes from patients with Hashimoto's thyroiditis have been cultured for 2--3 weeks in Marbrook flasks. During this period, readily detectable amounts of thyroglobulin and microsomal antibodies were synthesized by the cells and secreted into the culture medium. Gel filtration studies indicated that the autoantibodies produced in culture were of a similar molceular weight to the serum antibodies and this provided evidence that autoantibody synthesis in vitro was representative of autoantibody synthesis in vivo. Our data suggest that this culture technique may be used to make a detailed investigation of the human autoimmune disease process.