Additional monoclonal antibody (mAB) injections can replace thymic irradiation to allow induction of mixed chimerism and tolerance in mice receiving bone marrow transplantation after conditioning with anti-T cell mABs and 3-Gy whole body irradiation

While allogeneic bone marrow transplantation (BMT) has long been known to be capable of inducing donor-specific tolerance and hence permitting allograft acceptance without immunosuppressive pharmacotherapy, the toxicity of conditioning regimens required to achieve marrow engraftment has precluded the application of this approach to clinical organ transplantation. A relatively nontoxic method of conditioning mice that allows allogeneic bone marrow engraftment and induction of donor-specific skin allograft tolerance has recently been described. This regimen included anti-CD4 and anti-CD8 mAbs administered on day -5, followed by 3-Gy whole body irradiation (WBI) and 7-Gy thymic irradiation (TI) on day 0. To further reduce the potential toxicity of this regimen, we have now attempted to overcome the requirement for TI by administering additional mAb injections before and after BMT. Mixed chimerism and prolonged donor-specific skin graft acceptance were induced in 90% of B10 mice conditioned with anti-CD4 and -CD8 mAbs on days -6 and -1 and 3-Gy WBI on day 0 without TI. Despite long-term acceptance of donor-specific skin grafts, however, some of these animals showed a gradual decline in donor-type hematopoietic repopulation, and 2 of 10 mice regrafted with a second donor-type skin graft 5-9 months after BMT rejected the second and/or the original graft. This rejection after repeat donor-specific skin grafting correlated with a decline in the percentage of donor-type T cells between 6 and 12 weeks after BMT. In contrast, all animals receiving additional mAb injections 7 and 14 days following BMT after conditioning with mAbs on days -6 and -1 and 3-Gy WBI showed stable chimerism and accepted both primary and secondary donor-specific skin grafts. Animals receiving TI in addition to mAb and 3-Gy WBI also showed stable chimerism and long-term acceptance of initial (at 7 weeks) and later repeat donor-specific grafts. In contrast, the majority of mice receiving mAbs only on day -5 or on day -1 only, followed by 3-Gy WBI on day 0 without TI, did not accept initial donor-specific skin grafts, and showed only transient chimerism. Thus, the requirement for thymic irradiation to allow permanent mixed chimerism and donor-specific tolerance induction can be overcome by the administration of additional T cell-depleting mAb injections. These results establish a less toxic method of inducing donor-specific tolerance, thus increasing the potential clinical applicability of this approach to inducing organ allograft acceptance without chronic immunosuppressive therapy.

[Glucose intolerance after percutaneous ethanol injection therapy (PEI) in liver cirrhosis patients with hepatocellular carcinoma]

We studied the effect of percutaneous ethanol injection therapy (PEI) on glucose tolerance in liver cirrhosis patients with hepatocellular carcinoma. All of 10 patients underwent PEI and aspiration biopsy of the tumor on separate day. Two-time oral glucose tolerance tests (OGTT), before and after PEI, were performed in all patients. There were no significant changes in blood glucose and insulin chronologically measured on aspiration biopsy and PEI. To detect changes in glucose tolerance, we compared the results of OGTT before PEI with those of OGTT after PEI. On the basis of results of OGTT before PEI, patients were classified to impaired glucose tolerance group (4) and diabetes mellitus group (6). Blood glucose at 180 minutes on OGTT after PEI showed significantly higher value than that of OGTT before PEI, but insulin response was not suppressed. From these experiments we speculate that exaggerated insulin resistance due to injected ethanol may be one of the factors influencing glucose tolerance after PEI.

Correlation between integrin alpha 5 expression and the malignant phenotype of transitional cell carcinoma

We examined the expression of alpha 1, alpha 2, alpha 3, alpha 4, alpha 5 and beta 1 integrin on 36 transitional cell cancers (TCCs) in the bladder by immunohistochemistry. Only alpha 2, alpha 3 and beta 1 were detected on normal transitional cell epithelium, but four TCCs (12.5%) revealed positive staining for alpha 1, seven (19.4%) for alpha 4 and seven (20%) for alpha 5. These altered expressions of integrin alpha chain were more frequent in histologically higher stage or grade of TCC, and a correlation was found between increased alpha 5 expression and histological stage. alpha 5 was positive in 6 (35.3%) of 17 invasive TCCs whereas only 1 (5.9%) of 17 superficial TCCs. Flow cytometric analysis on bladder cancer cell lines showed that T24 and HT1376, which are undifferentiated TCC cell lines, highly expressed alpha 5 and beta 1. Also, SCaBER, which is derived from urinary bladder squamous cell cancer and which is recognised as the most malignant phenotype after metaplasia of transitional epithelium, had alpha 5 and beta 1. However, RT4, which is derived from transitional cell papilloma, showed no expression of alpha 5. Furthermore, reverse transcriptase-polymerase chain reaction (RT-PCR) showed the presence of mRNA of alpha 5 on T24, SCaBER and HT1376, but not on RT4. Taken together, it seems that the presence of alpha 5 integrin might be a more malignant phenotype in transitional cell carcinoma.

Antimutagenic activity of caffeic acid and related compounds

Effects of caffeic acid and chlorogenic acid on mutagenicity were studied using the Salmonella typhimurium system. These compounds had inhibitory effects on the mutagenicity of Trp-P-1 and Glu-P-2. Caffeic acid completely eliminated the mutagenicity induced by activated Glu-P-2. Some compounds analogous to caffeic acid, such as cinnamic acid, coumaric acid, and ferulic acid, also significantly decreased the mutagenicity of Glu-P-2.

Anti-CD4 monoclonal antibody reduces the dose of cyclophosphamide required to induce tolerance to H-2 haplotype identical skin allografts in mice

Cyclophosphamide (CP)-induced tolerance which consists of a single i.p. injection of 200 mg/kg CP 2 days after priming with 1 x 10(8) donor spleen cells (SC), leads to long-lasting donor-specific skin allograft tolerance in H-2 compatible, multiminor antigen incompatible, murine strain combinations. In this system, the optimal dose of CP has been suggested to be 200 mg/kg, however, such a dose of CP causes strong myelosuppression. In the present study, we therefore attempted to reduce the dose of CP by administering anti-CD4 monoclonal antibody (mAb) before donor cell priming in this tolerance-inducing system. When C3H/He (C3H; H-2k, Mls-1b) mice were injected i.p. with 200 micrograms anti-CD4 mAb on day -3, 1 x 10(8) AKR/J (AKR; H-2k, Mls-1a) SC plus 3 x 10(7) bone marrow cells (BMC) i.v. on day -2 and then 100 mg/kg CP i.p. on day 0, a long-lasting donor-specific skin allograft tolerance was established; furthermore, the decreases in the number of leukocytes and the concentration of hemoglobin (Hb) in the peripheral blood were all less in the C3H mice treated with this new combined protocol than in the C3H mice injected with 200 mg/kg CP following the previous protocol. In the periphery of these tolerant mice, the number of donor-reactive V beta 6+CD4+ T cells decreased and mixed chimerism was observed on both days 14 and 80. On the other hand, in the mice injected with AKR SC, BMC plus 100 mg/kg CP without anti-CD4 mAb, the number of V beta 6+CD4+ T cells decreased on day 14, and then recovered by day 80 when the mixed chimerism disappeared. These results therefore suggest that the combined use of anti-CD4 mAb with CP can reduce the dose of CP without affecting the efficiency of inducing donor-specific tolerance, probably due to the enhancement of the destruction effect of donor-reactive T cells by CP.

Epstein-Barr virus in Hodgkin's disease patients in Japan

BACKGROUND

The association of Epstein-Barr virus (EBV) and Hodgkin's disease (HD) has been suggested by serologic, epidemiologic, and molecular biologic studies. The high level of EBV association with HD in the developing countries was discussed in relation to the high HD incidence in these areas. Japanese HD shows a distinct peak incidence in older adults. In contrast, Western HD shows a bimodal pattern, the first peak in young adulthood and a second peak in older patients. In the present study, the EBV association with HD in Japan was investigated, and the results were compared with those reported from industrialized and developing countries.

METHODS

Fifty-seven patients with HD were studied for the presence or absence of the EBV genome by the polymerase chain reaction and in situ hybridization methods. Seven cases were excluded from the analysis for EBV because of poor preservation of nucleotides in the specimens.

RESULTS

EBV genomes were detected in the Reed-Sternberg (R-S) cells of 32 of the 50 patients examined (64%). The EBV association was independently affected by histologic subtype (84% in mixed cellularity and 44% in others), sex (76% in males and 31% in females), and age (76% in patients aged 40 years and older and 38% in patients younger than 40 years of age; P < 0.01). High EBV association is found at the peak in older adults predominantly with mixed cellularity type. Previous studies revealed that the high EBV was associated with the older peak of the bimodal peaks in Western HD, and a unimodal peak in childhood in developing countries. The EBV subtype was predominantly type A, which is identical to the immunocompetent type of HD reported previously.

CONCLUSIONS

The results of the current study, together with those reported previously, showed that the presence of the Epstein-Barr virus correlated with mixed cellularity type, age older than 40 years, and male sex.

Blood pressure and its regulation in spontaneously hypertensive rats bred on the lowest sodium diet for normal growth

To investigate the effects of dietary sodium restriction from conception to adulthood on blood pressure and its regulatory mechanisms, male offspring were derived from inbreeding in spontaneously hypertensive rats fed a diet containing sodium of 175 mumol/g food (control) or 22 mumol/g (low sodium), which is the least sodium content for normal growth. While urinary sodium excretion was markedly less, the low sodium diet did not inhibit body growth and failed to blunt the development of hypertension. Neither plasma catecholamine concentration nor depressor response to hexamethonium was different between the two groups at any age examined (8, 12, and 20 weeks). Plasma renin concentration was not elevated, whereas urinary excretion of aldosterone was increased at any age in the low sodium group compared with that in the control group. Other sets of rats were fed a diet containing sodium of 175 mumol/g plus mefruside (a diuretic) of 0.001% in the same manner as in the other two groups. Urinary sodium excretion per creatinine was higher than in the other groups. The diuretic treatment inhibited body growth and suppressed adult blood pressure. While the sympathetic function was not affected, both plasma renin concentration and urinary excretion of aldosterone were elevated. These results indicate that dietary sodium restriction with the least sodium for normal growth from conception cannot blunt either the sympathetic nervous function or the development of hypertension in spontaneously hypertensive rats. Aldosterone appears to play an important role in maintaining sodium homeostasis under the dietary sodium restriction.

Body surface distribution of significant changes in QRST time-integral values after radiofrequency catheter ablation in patients with Wolff-Parkinson-White syndrome

We analyzed 87-lead body surface QRST time-integral values (QRST values) in 29 patients with Wolff-Parkinson-White syndrome (group A, 17 patients with manifest left-sided accessory pathway; group B, 6 patients with manifest right-sided accessory pathway; and group C, 6 patients with concealed left-sided accessory pathway), before, 1 day after, and 1 week after radiofrequency catheter ablation (RCA). The number of leads with abnormal QRST values was significantly lower 1 week after RCA compared with those before RCA and 1 day after RCA in groups A and B (p < 0.05); there was no significant difference in QRST values before and 1 day after RCA in groups A and B. The QRST values over areas with preexisting repolarization abnormalities were significantly altered 1 week after RCA compared with before and 1 day after RCA in groups A and B (p < 0.01). However, there was no significant difference in the QRST values over areas without preexisting abnormalities before RCA. In group C, there were no significant differences in the QRST values or the number of leads with abnormal QRST values before, 1 day and 1 week after RCA. In conclusion, RCA did not significantly influence repolarization properties over areas without preexisting abnormalities, but gradually reduced preexisting repolarization abnormalities, which were closely related to the location of the accessory pathway in patients with manifest Wolff-Parkinson-White syndrome. Our results suggest that body surface QRST values are useful for assessment of repolarization abnormalities during the periablation period.

Prognostic indicators of major cardiac events in patients with asymptomatic coronary artery disease

We investigated the role of myocardial ischemia in acute myocardial infarction and cardiac death in 253 patients with asymptomatic coronary disease (206 men, 47 women, mean age: 55 +/- 8 years). Patients were divided into two groups: those with angina pectoris with no history of myocardial infarction (AP group, 93 patients) and those with a history of myocardial infarction (MI group, 160 patients). We also examined the usefulness of exercise electrocardiographic and Holter electrocardiographic findings as prognostic indicators of cardiac events. After 24-hour Holter electrocardiograms were obtained in both groups, patients were assigned to subgroups with or without silent myocardial ischemia (SMI) based on the presence or absence of transient ST-segment depression. Prognostic indicators were evaluated by multiple regression analysis. Cardiac events occurred in 26 (10.3%) of 253 patients; in 6 patients these events were fatal. The incidence of cardiac events was significantly higher in the SMI group than in the non-SMI group (16.4% versus 5.6%, p < 0.05). SMI was identified as a significant prognostic indicator in the overall population (p = 0.0088), as were the number of diseased coronary arteries in the AP group (p = 0.0152), and SMI (p = 0.0022) in the MI group. There were 3 deaths related to cardiac events in each group. The mean time from onset of angina pectoris to death was 73 +/- 41 months compared with 33 +/- 43 months in the MI group. Our findings suggest that the severity of the coronary lesion and SMI were important predictors of major cardiac events, and that the mechanism of the onset of cardiac events was different in the AP and MI groups.

Competitive chemiluminescent immunoassay for estradiol using an N-functionalized acridinium ester

We have compared three competitive chemiluminescent immunoassays (CLIA) for estradiol (E2) using an N-functionalized acridinium ester (AE). The assays were a standard competitive assay using immobilized antibody and directly labeled antigen (type A), an immobilized antibody and indirectly labeled antigen (type B), and an immobilized antigen and labeled antibody (type C). In an antibody-immobilized system, the assay using both AE- and E2-labeled thyroglobulin as a tracer (type B) was more sensitive than that using AE directly coupled with E2 (type A). Subsequently, a comparison of the antibody-immobilized system (type B) and an antigen-immobilized system (type C) showed that the latter was slightly more sensitive than the former. The sensitivity of the CLIA (type C) was similar or superior to commercially available CLIA or radioimmunoassays for E2. Thus, the N-functionalized AE proved to be a useful labeling reagent for a competitive CLIA with high sensitivity.

Clinical and physiological investigations in patients with taste abnormality

The cause of taste abnormality was investigated in 25 patients with decreased taste sensation (hypogeusia group) and 14 patients with abnormal taste sensation (dysgeusia group) by examining taste threshold, salivary flow rate, Candida cell culture, and laboratory examination of peripheral blood. The cause of hypogeusia was identified as iron deficiency in 7 patients, oral candidiasis in 6, hyposalivation (xerostomia) in 6, and psychiatric distress in 3, and could not be determined in 3 (idiopathic). Dysgeusia was associated with psychiatric distress in 8 patients, oral candidiasis in 3, drug medication in 2, and hyposalivation in 1. In the hypogeusia group, the decreased taste sensation generally corresponded with elevated taste thresholds, which decreased along with improvement of the decreased taste sensation in all except the 3 patients with psychiatric etiology and 2 of the 3 patients with idiopathic etiology. In contrast, no elevation or depression of taste thresholds were observed in the dysgeusia group, and the abnormal taste sensation did not disappear in most cases; however, drug-induced dysgeusia improved completely within 2 months after cessation of the drug administration. The serum copper and zinc levels were not decreased in any patient, but a decreased serum iron level was observed in 7 patients. Based on these results, it is concluded that abnormal taste sensation may be induced by many oral and systemic disturbances and that hypogeusia, which may be induced by deficiency of iron but not of zinc or copper, is usually accompanied by elevation of taste thresholds, while dysgeusia is not.

[Changes in nurses' knowledge and attitudes regarding AIDS in Mie Prefecture, Japan]

In 1990, we conducted a questionnaire survey showing that many nurses had incorrect knowledge of AIDS resulting in inappropriate attitudes toward AIDS patients. Following the first survey conducted in 1990, nurses were given various forms of AIDS education. The effectiveness of the AIDS education requires assessment. Therefore a second questionnaire survey was performed in 1993 to assess changes in nurses' knowledge and attitudes regarding AIDS. The same questionnaire as used in the first survey was sent to a random sample of nurses working at general hospitals in Mie Prefecture, Japan. The questionnaire covered knowledge of AIDS, psychological responses, attitudes and conduct around infected persons and measures against AIDS. Results of both questionnaire surveys showed that the majority of nurses acquired their knowledge predominantly from the mass media, and a large number of nurses worried that AIDS would spread in Japan. Almost half of the nurses were worried that they might be infected with AIDS. The second survey showed that nurses who acquired knowledge of AIDS from printed material, pamphlets and other educational resources, including lectures had increased. In 1993, many more nurses had accurate knowledge compared to the number in the first survey. In 1993 the number of nurses who discriminated against AIDS patients and HIV-infected persons had decreased.

Detection of point mutations in human tyrosinase gene by improved allele-specific amplification

Allele-specific amplification (ASA) is a simple and non-radioactive technique for detecting known point mutations that produce genetic diseases. Although this technique is based on the specific amplification of the target allele by a polymerase chain reaction (PCR) with allele-specific primers, the specificity of the amplification may depend on various PCR conditions. To avoid non-specific amplification which leads to false-positive results in ASA, we modified both the normal and mutant allele-specific primers so that they would have one constant base mismatch, located at the penultimate 3' position. We confirmed that our modification could inhibit such unfavorable amplification by using as templates genomic DNAs of patients affected with tyrosinase-negative oculocutaneous albinism (OCA). We then analyzed new patients affected with tyrosinase-negative OCA, and based the diagnosis on both the results of a clinical examination and those of a hair bulb test using ASA with the modified allele-specific primers. The results indicated that more than 3 alleles of the tyrosinase gene with a pathological mutation existed in Japanese patients.

MAT-1, a monoclonal antibody that specifically recognizes human tyrosinase

There is no available monoclonal antibody which reacts specifically recognizes human tyrosinase. Employing a synthetic peptide, MEKEDYHSLYQSHL, corresponding to the carboxyl terminus of human tyrosinase as an immunogen, we produced a mouse monoclonal antibody MAT-1 of the IgG1 isotype. The epitope for MAT-1 was determined to be EDYH, the sequence of which is not present in human tyrosinase-related protein-1 (TRP-1) or tyrosinase-related protein-2 (TRP-2). By transient expression assays and immunofluorescence technique, we show that MAT-1 reacts specifically with cells expressing human tyrosinase cDNA but not with cells expressing TRP-1 or TRP-2 cDNA. The results of immunohistochemical staining also confirmed that MAT-1 reacts specifically with epidermal melanocytes in human skin sections. MAT-1 should be invaluable for studying the interaction between tyrosinase and TRPs and for detecting the changes in the levels of tyrosinase expression. In addition, MAT-1 should be useful as a sensitive immunohistochemical tool for investigation of various pigmentary disorders and possibly for the diagnosis of melanoma.

A new method of estimating the distribution of muscle fiber conduction velocities

A computer-assisted method of estimating the distribution of muscle fiber conduction velocities is described. An electrode array composed of 2 stimulating and 4 recording electrodes is used to record surface muscle action potentials (MAPs) in response to direct muscle stimulation. The velocity distribution and the single muscle fiber action potential (SFAP) are calculated from the recorded MAPs by an iterative method of estimation. The estimation is based on the assumption that the spatial orientation of each muscle fiber viewed from the recording electrodes is the same along the muscle fibers and a MAP is recorded as a linear summation of all SFAPs. The accuracy of this estimation is demonstrated using simulated MAPs. The method is also tested on MAPs containing simulated amplifier noise, stimulus artifact, and errors in distance between electrodes. Finally we applied this method to MAP recordings of the biceps brachii in 23 healthy subjects. The velocity distribution was successfully estimated in 20 cases. The average of the estimated distributions was smaller than that described by previous workers. The reasons for the difference are discussed.

Mortality and morbidity rates, postoperative course, quality of life, and prognosis after extended radical lymphadenectomy for esophageal cancer. Comparison of three-field lymphadenectomy with two-field lymphadenectomy

PURPOSE

The authors evaluated the efficacy of extended radical (three-field) lymphadenectomy for esophageal cancer compared with less radical (two-field) lymphadenectomy. STUDY SUBJECTS AND ANALYTIC METHODS: The mortality and morbidity rates, postoperative courses, and survival rates were compared between 63 patients who underwent three-field lymph node dissection and 65 who underwent two-field lymph node dissection at Kurume University Hospital from 1986 to 1991. Long-term quality of life after surgery was compared between 37 patients who underwent three-field dissection and 35 who underwent two-field dissection from 1980 to 1991.

RESULTS

Three-field dissection resulted in better survival for patients with positive lymph node metastasis from a carcinoma in the upper thoracic or midthoracic esophagus compared with two-field dissection. The mortality rates, postoperative courses and quality of life were the same for both procedures.

CONCLUSIONS

Three-field dissection is preferred for upper thoracic or midthoracic esophageal cancer because of improved survival, acceptable mortality and morbidity rates, and good postoperative course and quality of life.

Deletion in the L1 open reading frame of human papillomavirus type 6a genomes associated with recurrent laryngeal papilloma

Human papillomavirus (HPV) type 6a genomes with a large deletion in their L1 open reading frames (ORF) were found in two of five recurrent cases of laryngeal papilloma. One of these mutant HPVs had a 186 base pair (bp) deletion near the N-terminus end of the L1 ORF, which encodes a major capsid protein. The other had a 454 bp deletion at the C-terminus end of L1 at which is located a nuclear localising signal (NLS). No other large deletion or insertion was found in the remaining regions of all five HPV6a genomes. The laryngeal papillomas which harboured the mutant viruses showed typical hyperplasia and pathological changes as observed in tumours induced by the wild-type virus. The biological significance of the two large deletions in the late region of HPV6a associated with laryngeal papilloma is discussed.

Molecular cloning of two types of cDNA encoding subunit RC6-I of rat proteasomes

A new subunit, named RC6-I, of the rat 20 S proteasome was purified and the partial amino acid sequences of several peptide fragments obtained by digestion with lysyl-endopeptidase were determined by Edman degradation. Amplification of cDNAs encoding RC6-I by the polymerase chain reaction (PCR) technique revealed two types of cDNA, tentatively designated as RC6-IL and RC6-IS in order of size. The nucleotide sequences of the two cDNAs are identical except that RC6-IL contains an insertion of 18 nucleotides in the coding region compared with RC6-IS. The polypeptide predicted from the open reading frame of RC6-IS cDNA consists of 248 amino acid residues with a calculated molecular weight of 27,783. These values are consistent with those obtained by protein chemical analyses. Computer-assisted homology analysis showed that RC6-I belongs to the alpha-type subfamily of the proteasome gene family, which shows similarity to the alpha-subunit of the archaebacterium Thermoplasma acidophilum proteasome, and that the 18 nucleotide insert, encoding six amino acid residues, VVASVS, appears to be unique to RC6-IL, because this motif has not been conserved in any other alpha-type subunit. By reverse transcription (RT)-PCR analysis, the mRNAs for both RC6-IL and RC6-IS were found in all the rat tissues examined. These results suggest that proteasomes are present as a heterogeneous population, possibly for acquisition of diversity of functions.

Inhibitory effect of c-fos overexpression on B cell proliferative responses to membrane IGM cross-linking

Constitutive expression of the c-fos gene perturbs the de novo synthesis of RNA and DNA in B cells stimulated by surface immunoglobulin (sIg) cross-linking. In order to examine kinetics of the regulatory effect on the activation process of B cells, we used splenic B cells from transgenic mice carrying the c-fos gene under the control of the interferon alpha/beta (IFN)-inducible Mx gene promoter (Mx-c-fos). In the absence of IFN, Mx-c-fos B cells proliferated well by anti-IgM stimulation. However, both RNA and DNA synthesis in the Mx-c-fos B cells were markedly reduced by the addition of IFN in the culture within 12 h after anti-IgM stimulation. These results suggest that this regulatory effect of c-Fos displays at the mid G1 phase of the cell cycle.

Astaxanthin, a carotenoid without vitamin A activity, augments antibody responses in cultures including T-helper cell clones and suboptimal doses of antigen

Astaxanthin, a carotenoid without vitamin A activity, enhances T-dependent antigen (Ag)-specific humoral immune responses. We examined carotenoid actions on T-helper (Th) cell activity in a direct manner with reconstitution experiments; spleen Th cells were replaced with Ag-specific Type 1 and Type 2 (Th1 and Th2) Th cell clones. The Ag for the Th1 and Th2 clones were pigeon cytochrome C and rabbit gamma-globulin, respectively. Astaxanthin and beta-carotene augmented the number of IgM antibody (Ab)-secreting cells when unprimed B cells were incubated with Th clones and stimulated with suboptimal doses of Ag specific for each Th clone. The number of IgG Ab-secreting cells were greater with use of in vivo primed B cells than with unprimed B cells in both Th clones. Astaxanthin but not beta-carotene augmented the number of IgG Ab-secreting cells when primed B cells and Th cell clones were stimulated with suboptimal doses of Ag specific for each Th clone. In the presence of optimal doses of Ag for each Th clone, neither carotenoid augmented the number of Ab-secreting cells. Astaxanthin and beta-carotene may enhance the actions of both Th1 and Th2 cells for humoral immune responses with suboptimal Ag challenges; certain carotenoids may help maintain Ag-mediated immune responses at optimal levels.