Effects of a Mindfulness-Based Intervention on Distress, Weight Gain, and Glucose Control for Pregnant Low-Income Women: A Quasi-Experimental Trial Using the ORBIT Model

Background

Stress can lead to excessive weight gain. Mindfulness-based stress reduction that incorporates mindful eating shows promise for reducing stress, overeating, and improving glucose control. No interventions have tested mindfulness training with a focus on healthy eating and weight gain during pregnancy, a period of common excessive weight gain. Here, we test the effectiveness of such an intervention, the Mindful Moms Training (MMT), on perceived stress, eating behaviors, and gestational weight gain in a high-risk sample of low income women with overweight/obesity.

Method

We conducted a quasi-experimental study assigning 115 pregnant women to MMT for 8 weeks and comparing them to 105 sociodemographically and weight equivalent pregnant women receiving treatment as usual. Our main outcomes included weight gain (primary outcome), perceived stress, and depression.

Results

Women in MMT showed significant reductions in perceived stress (β = − 0.16) and depressive symptoms (β = − 0.21) compared to the treatment as usual (TAU) control group. Consistent with national norms, the majority of women (68%) gained excessive weight according to Institute of Medicine weight-gain categories, regardless of group. Slightly more women in the MMT group gained below the recommendation. Among secondary outcomes, women in MMT reported increased physical activity (β = 0.26) and had lower glucose post-oral glucose tolerance test (β = − 0.23), being 66% less likely to have impaired glucose tolerance, compared to the TAU group.

Conclusion

A short-term intervention led to significant improvements in stress, and showed promise for preventing glucose intolerance. However, the majority of women gained excessive weight. A longer more intensive intervention may be needed for this high-risk population.

Clinical Trials.gov #NCT01307683.

Effects of a mindfulness-based intervention on mindful eating, sweets consumption, and fasting glucose levels in obese adults: data from the SHINE randomized controlled trial

We evaluated changes in mindful eating as a potential mechanism underlying the effects of a mindfulness-based intervention for weight loss on eating of sweet foods and fasting glucose levels. We randomized 194 obese individuals (M age = 47.0 ± 12.7 years; BMI = 35.5 ± 3.6; 78% women) to a 5.5-month diet-exercise program with or without mindfulness training. The mindfulness group, relative to the active control group, evidenced increases in mindful eating and maintenance of fasting glucose from baseline to 12-month assessment. Increases in mindful eating were associated with decreased eating of sweets and fasting glucose levels among mindfulness group participants, but this association was not statistically significant among active control group participants. Twelve-month increases in mindful eating partially mediated the effect of intervention arm on changes in fasting glucose levels from baseline to 12-month assessment. Increases in mindful eating may contribute to the effects of mindfulness-based weight loss interventions on eating of sweets and fasting glucose levels.

Effects of a mindfulness-based weight loss intervention in adults with obesity: A randomized clinical trial

OBJECTIVE

To determine whether adding mindfulness-based eating and stress management practices to a diet-exercise program improves weight loss and metabolic syndrome components.

METHODS

In this study 194 adults with obesity were randomized to a 5.5-month program with or without mindfulness training and identical diet-exercise guidelines. Intention-to-treat analyses with multiple imputation were used for missing data. The primary outcome was 18-month weight change.

RESULTS

Estimated effects comparing the mindfulness to control arm favored the mindfulness arm in (a) weight loss at 12 months, -1.9 kg (95% CI: -4.5, 0.8; P = 0.17), and 18 months, -1.7 kg (95% CI: -4.7, 1.2; P = 0.24), though not statistically significant; (b) changes in fasting glucose at 12 months, -3.1 mg/dl (95% CI: -6.3, 0.1; P = 0.06), and 18 months, -4.1 mg/dl (95% CI: -7.3, -0.9; P = 0.01); and (c) changes in triglyceride/HDL ratio at 12 months, -0.57 (95% CI: -0.95, -0.18; P = 0.004), and 18 months, -0.36 (95% CI: -0.74, 0.03; P = 0.07). Estimates for other metabolic risk factors were not statistically significant, including waist circumference, blood pressure, and C-reactive protein.

CONCLUSIONS

Mindfulness enhancements to a diet-exercise program did not show substantial weight loss benefit but may promote long-term improvement in some aspects of metabolic health in obesity that requires further study.

Reduced reward-driven eating accounts for the impact of a mindfulness-based diet and exercise intervention on weight loss: Data from the SHINE randomized controlled trial

Many individuals with obesity report over eating despite intentions to maintain or lose weight. Two barriers to long-term weight loss are reward-driven eating, which is characterized by a lack of control over eating, a preoccupation with food, and a lack of satiety; and psychological stress. Mindfulness training may address these barriers by promoting awareness of hunger and satiety cues, self-regulatory control, and stress reduction. We examined these two barriers as potential mediators of weight loss in the Supporting Health by Integrating Nutrition and Exercise (SHINE) randomized controlled trial, which compared the effects of a 5.5-month diet and exercise intervention with or without mindfulness training on weight loss among adults with obesity. Intention-to-treat multiple mediation models tested whether post-intervention reward-driven eating and psychological stress mediated the impact of intervention arm on weight loss at 12- and 18-months post-baseline among 194 adults with obesity (BMI: 30-45). Mindfulness (relative to control) participants had significant reductions in reward-driven eating at 6 months (post-intervention), which, in turn, predicted weight loss at 12 months. Post-intervention reward-driven eating mediated 47.1% of the total intervention arm effect on weight loss at 12 months [β = -0.06, SE(β) = 0.03, p = .030, 95% CI (-0.12, -0.01)]. This mediated effect was reduced when predicting weight loss at 18 months (p = .396), accounting for 23.0% of the total intervention effect, despite similar weight loss at 12 months. Psychological stress did not mediate the effect of intervention arm on weight loss at 12 or 18 months. In conclusion, reducing reward-driven eating, which can be achieved using a diet and exercise intervention that includes mindfulness training, may promote weight loss (clinicaltrials.gov registration: NCT00960414).

Putting the brakes on the "drive to eat": Pilot effects of naltrexone and reward-based eating on food cravings among obese women

PURPOSE

Obese individuals vary in their experience of food cravings and tendency to engage in reward-driven eating, both of which can be modulated by the neural reward system rather than physiological hunger. We examined two predictions in a sample of obese women: (1) whether opioidergic blockade reduced food-craving intensity, and (2) whether opioidergic blockade reduced an association between food-craving intensity and reward-driven eating, which is a trait-like index of three factors (lack of control over eating, lack of satiation, preoccupation with food).

METHODS

Forty-four obese, pre-menopausal women completed the Reward-Based Eating Drive (RED) scale at study start and daily food-craving intensity on 5 days on which they ingested either a pill-placebo (2 days), a 25 mg naltrexone dose (1 day), or a standard 50mg naltrexone dose (2 days).

RESULTS

Craving intensity was similar under naltrexone and placebo doses. The association between food-craving intensity and reward-driven eating significantly differed between placebo and 50mg naltrexone doses. Reward-driven eating and craving intensity were significantly positively associated under both placebo doses. As predicted, opioidergic blockade (for both doses 25mg and 50mg naltrexone) reduced the positive association between reward-driven eating and craving intensity to non-significance.

CONCLUSIONS

Opioidergic blockade did not reduce craving intensity; however, blockade reduced an association between trait-like reward-driven eating and daily food-craving intensity, and may help identify an important endophenotype within obesity.

Acute responses to opioidergic blockade as a biomarker of hedonic eating among obese women enrolled in a mindfulness-based weight loss intervention trial

There are currently no commonly used or easily accessible 'biomarkers' of hedonic eating. Physiologic responses to acute opioidergic blockade, indexed by cortisol changes and nausea, may represent indirect functional measures of opioid-mediated hedonic eating drive and predict weight loss following a mindfulness-based intervention for stress eating. In the current study, we tested whether cortisol and nausea responses induced by oral ingestion of an opioidergic antagonist (naltrexone) correlated with weight and self-report measures of hedonic eating and predicted changes in these measures following a mindfulness-based weight loss intervention. Obese women (N = 88; age = 46.7 ± 13.2 years; BMI = 35.8 ± 3.8) elected to complete an optional sub-study prior to a 5.5-month weight loss intervention with or without mindfulness training. On two separate days, participants ingested naltrexone and placebo pills, collected saliva samples, and reported nausea levels. Supporting previous findings, naltrexone-induced cortisol increases were associated with greater hedonic eating (greater food addiction symptoms and reward-driven eating) and less mindful eating. Among participants with larger cortisol increases (+1 SD above mean), mindfulness participants (relative to control participants) reported greater reductions in food addiction symptoms, b = -0.95, SE(b) = 0.40, 95% CI [-1.74, -0.15], p = .021. Naltrexone-induced nausea was marginally associated with reward-based eating. Among participants who endorsed naltrexone-induced nausea (n = 38), mindfulness participants (relative to control participants) reported greater reductions in food addiction symptoms, b = -1.00, 95% CI [-1.85, -0.77], p = .024, and trended toward reduced reward-based eating, binge eating, and weight, post-intervention. Single assessments of naltrexone-induced cortisol increases and nausea responses may be useful time- and cost-effective biological markers to identify obese individuals with greater opioid-mediated hedonic eating drive who may benefit from weight loss interventions with adjuvant mindfulness training that targets hedonic eating.

Satiety-related hormonal dysregulation in behavioral variant frontotemporal dementia

OBJECTIVE

To investigate whether patients with behavioral variant frontotemporal dementia (bvFTD) have dysregulation in satiety-related hormonal signaling using a laboratory-based case-control study.

METHODS

Fifty-four participants (19 patients with bvFTD, 17 patients with Alzheimer disease dementia, and 18 healthy normal controls [NCs]) were recruited from a tertiary-care dementia clinic. During a standardized breakfast, blood was drawn before, during, and after the breakfast protocol to quantify levels of peripheral satiety-related hormones (ghrelin, cortisol, insulin, leptin, and peptide YY) and glucose. To further explore the role of patients' feeding abnormalities on hormone levels, patients were classified into overeating and nonovereating subgroups based on feeding behavior during separate laboratory-based standardized lunch feeding sessions.

RESULTS

Irrespective of their feeding behavior in the laboratory, patients with bvFTD, but not patients with Alzheimer disease dementia, have significantly lower levels of ghrelin and cortisol and higher levels of insulin compared with NCs. Furthermore, while laboratory feeding behavior did not predict alterations in levels of ghrelin, cortisol, and insulin, only patients with bvFTD who significantly overate in the laboratory demonstrated significantly higher levels of leptin compared with NCs, suggesting that leptin may be sensitive to particularly severe feeding abnormalities in bvFTD.

CONCLUSIONS

Despite a tendency to overeat, patients with bvFTD have a hormonal profile that should decrease food intake. Aberrant hormone levels may represent a compensatory response to the behavioral or neuroanatomical abnormalities of bvFTD.

A new biomarker of hedonic eating? A preliminary investigation of cortisol and nausea responses to acute opioid blockade

Overweight and obese individuals differ in their degree of hedonic eating. This may reflect adaptations in reward-related neural circuits, regulated in part by opioidergic activity. We examined an indirect, functional measure of central opioidergic activity by assessing cortisol and nausea responses to acute opioid blockade using the opioid antagonist naltrexone in overweight/obese women (mean BMI=31.1±4.8) prior to the start of a mindfulness-based intervention to reduce stress eating. In addition, we assessed indices of hedonic-related eating, including eating behaviors (binge eating, emotional eating, external eating, restraint) and intake of sweets/desserts and carbohydrates (Block Food Frequency); interoceptive awareness (which is associated with dysregulated eating behavior); and level of adiposity at baseline. Naltrexone-induced increases in cortisol were associated with greater emotional and restrained eating and lower interoceptive awareness. Naltrexone-induced nausea was associated with binge eating and higher adiposity. Furthermore, in a small exploratory analysis, naltrexone-induced nausea predicted treatment response to the mindfulness intervention, as participants with more severe nausea at baseline maintained weight whereas those with little or no nausea responses tended to gain weight. These preliminary data suggest that naltrexone-induced cortisol release and nausea may help identify individuals who have greater underlying food reward dependence, which leads to an excessive drive to eat. Future research is needed to confirm this finding and to test if these markers of opioidergic tone might help predict success in certain types of weight management programs.

An siRNA screen identifies RSK1 as a key modulator of lung cancer metastasis

We performed a kinome-wide siRNA screen and identified 70 kinases altering cell migration in A549 lung cancer cells. In particular, ribosomal S6 kinase 1 (RSK1) silencing increased, whereas RSK2 and RSK4 downregulation inhibited cell motility. In a secondary collagen-based three-dimensional invasion screen, 38 of our hits cross-validated, including RSK1 and RSK4. In two further lung cancer cell lines, RSK1 but not RSK4 silencing showed identical modulation of cell motility. We therefore selected RSK1 for further investigation. Bioinformatic analysis followed by co-immunoprecipitation-based validation revealed that the actin regulators VASP and Mena interact with RSK1. Moreover, RSK1 phosphorylated VASP on T278, a site regulating its binding to actin. In addition, silencing of RSK1 enhanced the metastatic potential of these cells in vivo using a zebrafish model. Finally, we investigated the relevance of this finding in human lung cancer samples. In isogenically matched tissue, RSK1 was reduced in metastatic versus primary lung cancer lesions. Moreover, patients with RSK1-negative lung tumours showed increased number of metastases. Our results suggest that the findings of our high-throughput in vitro screen can reliably identify relevant clinical targets and as a proof of principle, RSK1 may provide a biomarker for metastasis in lung cancer patients.

Endogenous ACTH, not only alpha-melanocyte-stimulating hormone, reduces food intake mediated by hypothalamic mechanisms

ACTH and alpha-melanocyte-stimulating hormone (alpha-MSH) are both consecutively processed from proopiomelanocortin (POMC), which is synthesized in hypothalamic arcuate neurons innervating the paraventricular nuclei (PVN). POMC secretion/synthesis is regulated by energy availability. ACTH and alpha-MSH bind with equal affinity to melanocortin-4 receptors and elicit similar effects on signal transduction in-vitro. Endogenous alpha-MSH thus far is believed to be the major physiological agonist and to act in an anorexigenic manner. Until now, it was fully unknown whether endogenous ACTH is also involved in the regulation of appetite and food intake. In this study in rats, we now show that icv ACTH as well as alpha-MSH possess anorexigenic effects in the PVN or areas in close proximity in vivo and that the effect of ACTH is direct and not mediated via alpha-MSH. We investigated the roles of endogenous ACTH and alpha-MSH by PVN application of the respective antibodies under different physiological conditions. In satiated rats with high levels of ACTH and alpha-MSH in the PVN, antibody administration increased food intake and body weight gain; hungry animals were unaffected. Finally, repeated injections of ACTH antibodies into PVN resulted in persistently increased food intake during the light period. These data now provide robust evidence that endogenous ACTH without further processing acts in the PVN or areas in close proximity to reduce food intake under conditions of feeding-induced satiety.

Role of CD4+ and CD8+ T cells in early and late acute rejection of small bowel allograft

BACKGROUND/PURPOSE

Results of small bowel transplantation remain unsatisfactory because of severe immune rejection. The current study aims to elucidate the role of activation of CD4+ and CD8+ T cells in early and late acute rejection of small bowel allograft and, hence, provide the immunologic basis for developing new therapeutic strategies.

METHODS

We used an MHC fully mismatched (DA to Lewis) heterotopic rat small bowel transplant model and a unique FK506-based immunosuppressive regimen, which suppresses early acute rejection but does not prevent late acute rejection. Flow cytometric analysis was used to quantitate the number of activated CD4+ and CD8+ T cells in graft and host mesenteric lymph nodes.

RESULTS

The survival (mean +/- SD) of intestinal allograft was significantly prolonged, from 6.6 +/- 0.84 days for the untreated group to 40.7 +/- 14.1 days for the FK506-treated group. Activation of CD4+ cells was suppressed significantly in the FK506-treated group on postoperative day 7 compared with the untreated group (29.4% +/- 3.55% v 52.83% +/- 11.9%; P <.01). Activation of CD8+ cells was similarly suppressed (31.5 +/- 10.34% v 48.53 +/- 14.34%; P <.05). Interestingly, at late acute rejection, activated CD4+ and CD8+ T cells remained at almost the same low levels as those on postoperative day 7 in the FK506-treated group. The spleen to body weight ratio was significantly increased in the untreated group (0.53 +/- 0.07), and slightly increased in the FK treated group (0.27 +/- 0.07, on postoperative day 7; 0.24 +/- 0.07 at late acute rejection) compared with the syngeneic group (0.18 +/- 0.02).

CONCLUSION

The activation of CD4+ and CD8+ T cells was suppressed effectively by early potent immunosuppressive treatment resulting in prolonged survival of intestinal allograft. At late acute rejection, the CD4+ and CD8+ T cells remained at low-level activation status, in contrast to the surge of CD4+ and CD8+ activation during early acute rejection. This suggests that persistent T cell activation even at low level is sufficient to cause the late acute rejection eventually. A therapeutic strategy targeting these cells is needed for long-term engraftment.

Recipient FK506 pretreatment regimens in rat small bowel transplantation: allograft survival, function, and systemic infection

PURPOSE

Successful small bowel transplantation requires effective immunosuppression that preserves intestinal function but avoids opportunistic infection. This study aims to evaluate FK506 as a single immunosuppressant in different pretreatment regimens in a rat high responder strain combination.

METHODS

Lewis --> DA rat heterotopic small bowel transplantation was performed. Studied groups were (1) untreated control, n = 12; (2) FK-1, n = 8; (3) FK-3, n = 8. FK506 (2 mg/kg/d, intramuscularly) was given to the recipients for 1 day (FK-1) and 3 days (FK-3) before small bowel transplantation, followed by 2 weeks of subtherapeutic treatment (0.3 mg/kg/d, intramuscularly) after small bowel transplantation. Syngeneic small bowel transplantation also was performed (n = 8). FK blood levels, maltose absorption test, histology, and bacteriology were performed at different postoperative days.

RESULTS

Allograft survival was prolonged significantly with FK pretreatment, being more so in FK-3 group (FK-1, 22.2 +/- 1.5 d; FK-3, 40.7 +/- 14.1 d; control, 6.6 +/- 0.8 d; P< .01). In the first postoperative week, FK blood level was significantly higher in FK-3 group (19.8 +/- 1.5 ng/mL) than in FK-1 group (5.0 +/- 0.4 ng/mL; P < .05). There was no evidence of systemic infection in either FK-treated group. For maltose absorption, control allograft was abnormal on day 7 correlating to severely damaged intestinal architecture. In contrast, FK-treated allografts showed well-protected intestinal structure and normal absorption on days 7 and 21.

CONCLUSION

High FK506 blood levels in the first postoperative week, achieved with FK pretreatment, prolonged intestinal allograft survival and preserved intestinal structure and function without allowing systemic infection.

The activity of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system in relation to waist/hip circumference ratio in men

OBJECTIVE

To investigate possible differences, between generally and abdominally obese men, in activity and regulation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system.

RESEARCH METHODS AND PROCEDURES

Fifty non-diabetic, middle-aged men were selected to obtain two groups with similar body mass index (BMI) but different waist/hip circumference ratio (WHR). Measurements were performed of the activity of the HPA axis and the sympathetic nervous system, as well as metabolic and endocrine variables.

RESULTS

Men with a high WHR, in comparisons with men with a low WHR, had higher insulin, glucose, and triglyceride values in the basal state and higher glucose and insulin after an oral glucose tolerance test. Men with high WHR had elevated diurnal adrenocorticotropic hormone (ACTH) values but similar cortisol values, except lower cortisol values in the morning. Diurnal growth hormone concentrations showed reduced peak size. Stimulation of the HPA axis with corticotropin-releasing hormone (CRH) and laboratory stress showed no difference in ACTH values between groups, but cortisol values were lower in men with high WHR. In comparison with men with a low WHR, men with a high WHR had elevated pulse pressure and heart rate in the basal state and after challenges by CRH and laboratory stress. They also had increased urinary excretion of catecholamine metabolites.

DISCUSSION

These results suggest a mild dysregulation of the HPA axis, occurring with elevated WHR independent of the BMI. The results also indicate a central activation of the sympathetic nervous system, such as in the early phases of hypertension, correlating with insulin resistance.

Neuroanatomical basis for facilitation of hypothalamic-pituitary-adrenal responses to a novel stressor after chronic stress

Animals exposed to chronic stress exhibit normal or enhanced hypothalamic-pituitary adrenal responses to novel, acute stimuli despite the inhibitory endogenous corticosteroid response to the chronic stressor. Prior stress is thought to induce a central facilitatory trace that, upon exposure to a novel stimulus, balances or overcomes the inhibitory effects of corticosterone. The neuroanatomical basis for this facilitation of hypothalamic pituitary adrenal responses is unknown. In this study, we first show increased adrenocorticotropin and corticosterone responses to the novel stressor of restraint in rats exposed to intermittent cold for seven days. We then compared numbers of Fos-immunoreactive cells in 26 sites in control and chronically stressed rats at various times after onset of a 30 min restraint. At 60 min, density of Fos-stained cells was significantly higher in chronically stressed than in control rats in the parabrachial/Kölliker-Fuse area, posterior paraventricular thalamus, central, basolateral and basomedial nuclei of the amygdala and parvocellular paraventricular hypothalamus. The posterior paraventricular nucleus of the thalamus receives projections from the parabrachial nucleus and projects heavily to the differentially stained subnuclei of the amygdala, which in turn project to the parvocellular paraventricular nucleus of the hypothalamus. We propose that increased activity in the parabrachial-posterior paraventricular thalamus-amygdala-parvocellular paraventricular hypothalamus underlies facilitation of the hypothalamic pituitary-adrenal axis to novel stress in chronically stressed rats. We confirmed part of this proposal by showing that lesions of the posterior paraventricular nucleus of the thalamus increase adrenocorticotropin responses to restraint only in previously chronically stressed animals. This potential circuit provides a basis for further examination of the functional roles of these regions in stress-induced facilitation of hypothalamic pituitary-adrenal activity.

Type II collagen-reactive T cell clones from mice with collagen-induced arthritis

Certain strains of mice develop a symmetrical polyarthritis after immunization with type II collagen. The incidence of arthritis after such immunization is variable. To study the arthritogenic potential of T cells reactive with type II collagen, we isolated draining lymph node cells from mice that had developed arthritis after immunization with bovine type II collagen. From these immune lymph node cells we were able to clone T cells reactive with type II collagen. Two separate sets of T cell clones were isolated. The first set reacted with either native bovine or native chick type II collagen, but did not react with type I collagen. The second set of T cell clones reacted with bovine type II collagen, but did not respond to either native chick type II collagen or type I collagen. These clones will be tested for their influence on the development of arthritis in vivo.

Type II collagen-reactive T cell clones from mice with collagen-induced arthritis

Certain strains of mice develop a symmetrical polyarthritis after immunization with type II collagen. The incidence of arthritis after such immunization is variable. To study the arthritogenic potential of T cells reactive with type II collagen, we isolated draining lymph node cells from mice that had developed arthritis after immunization with bovine type II collagen. From these immune lymph node cells we were able to clone T cells reactive with type II collagen. Two separate sets of T cell clones were isolated. The first set reacted with either native bovine or native chick type II collagen, but did not react with type I collagen. The second set of T cell clones reacted with bovine type II collagen, but did not respond to either native chick type II collagen or type I collagen. These clones will be tested for their influence on the development of arthritis in vivo.

Regulation of ACTH and cortisol in depression

Disturbances of hypothalamic-pituitary-adrenal regulation are frequently observed in a subgroup of patients suffering from major depression. The mechanism of hypothesized pituitary and hypothalamic involvement in this dysregulation remains relatively uncharacterized. In this paper we investigated the response of adrenocorticotropin (ACTH), as well as cortisol, to dexamethasone inhibition and characterized the dynamic response of ACTH to a one-hour infusion of cortisol in normal subjects and patients suffering from depression. A paradoxical increase in ACTH in response to cortisol is noted in one patient.

Early rheumatoid-like lesions in rabbits injected with foreign serum. V. Attempted super-imposition of allergization to cartilage collagen

Intradermal injection of bovine articular type II collagen produced, as expected, joint lesions in rats. However, this collagen preparation failed (1) to produce joint lesions in rabbits or (2) to exacerbate joint lesions in rabbits formed in the serum sickness model. Collagen extracted from rabbit xiphoid cartilage failed to show arthritogenic properties on intradermal injection in either rats or rabbits. It also failed to exacerbate joint lesions in the serum sickness model.

Anti-erythrocyte autoantibody production in mice associated with the injection of rat erythrocytes

Mice injected with rat erythrocytes developed anti-erythrocyte autoantibodies which reached a plateau at 4-12 weeks, then gradually declined until at about 24 weeks the majority of mice were negative. In such recovered mice re-challenge with rat erythrocytes produced an accelerated peak of autoantibody and a much more rapid return to a Coombs' negative state. The auto-antibody response was distinguished from the anti-rat response in being more radio-sensitive. Purified autoantibody reacted to higher titre with rat than with syngeneic erythrocytes. Lymphoid cells, from mice given rat erythrocytes (but not sheep, rabbit or guinea-pig erythrocytes) transferred to normal syngeneic recipients given rat erythrocytes suppressed autoantibody production in the recipients. This suppression was much more effective against the autoantibody response than against the response to the inducing cross-reactive antigen; and the degree of suppression was related to the number of cells transferred and to their time of administration relative to the injection of rat erythrocytes. The induction of autoantibody and the generation of suppressor cells in donor animals was unaffected by adult thymectomy. A comparison of the effect of anti-rat erythrocyte antibodies and spleen cells from rat-immunized donors on recipients responses to rat erythrocytes revealed that whereas anti-rat antibodies suppressed both the autoantibody and the anti-rat responses, the spleen cells suppressed only the autoantibody response. Populations of spleen cells, from rat immunized donors, depleted of B cells retained their suppressive activity, whereas the suppressive efficacy of T-cell depleted populations was reduced but not abolished. It is suggested that T cells can specifically interfere with thesponse of autoreactive B cells, although non-T cells (possibly B cells acting by an antibody-feedback mechanism) can also suppress their response.