Significant accumulation of KRAS mutations in bronchiolar metaplasia-associated honeycomb lesions of interstitial pneumonia.

Interstitial pneumonia (IP) is a major risk factor for lung adenocarcinoma (LADC). IP-related LADC predominantly develops in the bronchiolar metaplasia lining in honeycomb lesions. Kirsten rat sarcoma virus (KRAS) is the most common oncogene mutated in IP-related LADC. The present study examined the metaplastic epithelia in honeycomb lesions for KRAS mutations using digital droplet polymerase chain reaction (ddPCR), a sensitive method used to detect infrequent mutations. Significantly higher KRAS mutation variant allele frequencies (VAFs) were detected in the metaplastic lung epithelia from 13 patients with IP compared with those in 46 non-lesioned lung samples from patients without IP (G12V, P=0.0004, G12C, P=0.0181, and G12A, P=0.0234; Mann Whitney U test). Multivariate analyses revealed that higher KRAS G12V (logistic regression model; P=0.0133, odds ratio=7.11) and G12C (P=0.0191, odds ratio=5.81) VAFs in patients with IP were independent of confounding variables, such as smoking and age. In patients with IP, metaplastic epithelia exhibited significantly higher KRAS G12V and G12C VAFs compared with the non-lesioned counterparts (paired t-test; G12V, P=0.0158, G12C, P=0.0465). These results suggested that IP could increase KRAS mutations and supported the hypothesis that bronchiolar metaplasia could be a precursor for IP-related LADC.

Implications of thyroid transcription factor-1 gene methylation in carcinogenesis of interstitial pneumonia-related non-terminal respiratory unit lung adenocarcinoma.

The present study aimed to elucidate the mechanisms underlying the histogenesis of interstitial pneumonia (IP)-related lung adenocarcinoma (LADC). We focused on the methylation of thyroid transcription factor 1 (TTF-1). The TTF-1 locus was highly methylated in IP-LADCs compared to non-IP-LADCs. Among the IP-LADCs, the non-terminal respiratory unit (TRU) LADCs showed marked hypermethylation in CpG sites in a particular intragenic region. This region was also found to be highly methylated in the IP lungs. The hierarchical dendrogram based on methylation levels divided the IP lungs into three different clusters. One of them showed a methylation profile similar to that of non-TRU LADCs. The non-TRU LADCs developed from this cluster with a significantly higher frequency. Moreover, bronchiolar metaplasia lining honeycomb/cystic lesions in IP lungs, IP-related non-TRU LADCs, and bronchiolar epithelia in healthy lungs were separately collected by microdissection and examined for methylation. Bronchiolar metaplasia showed hypermethylation, but bronchiolar epithelia did not. The methylation patterns in bronchiolar metaplasia were similar to those in non-TRU LADCs. In summary, a particular region of TTF-1 was highly methylated in IP-related non-TRU LADCs and bronchiolar metaplasia, supporting the theory that IP-related non-TRU LADCs may develop from bronchiolar metaplasia lining honeycomb/cystic lesions.

Frequent DYRK2 gene amplification in micropapillary element of lung adenocarcinoma - an implication in progression in EGFR-mutated lung adenocarcinoma.

The present study aimed to discern the molecular alterations involved in the progression of EGFR-mutated lung adenocarcinoma (LADC). We previously demonstrated that the micropapillary (mPAP) element is the most important histological factor for assessing malignant grades in LADCs. Therefore, mPAP and other elements were separately collected from three cases of EGFR-mutated LADC using laser capture microdissection and subjected to a comprehensive mRNA expression analysis. We focused on DYRK2 in this study because its level showed a substantial increase in EGFR-mutated LADCs with mPAP. We also immunohistochemically examined 130 tumors for the expression of DYRK2. The results confirmed a strong expression of DYRK2 in EGFR-mutated LADC with mPAP. Fluorescent in situ hybridization (FISH) analyses targeting the DYRK2 locus revealed frequent gene amplification in EGFR-mutated LADC, specifically occurring in the high-grade components, like mPAP. In summary, the results of this study suggest that DYRK2 overexpression through gene amplification is one of the molecular mechanisms responsible for promoting the progression of EGFR-mutated LADC.

Antibiotic de-escalation therapy in patients with community-acquired nonbacteremic pneumococcal pneumonia.

Background De-escalation therapy is recommended as an effective antibiotic treatment strategy for several infectious diseases. While there is limited evidence supporting its clinical and cost-effective outcomes in patients with community-acquired bacteremic pneumonia, there is no evidence in patients with nonbacteremic pneumonia. Objective This study aimed to evaluate the antibiotic costs in patients who did and did not receive de-escalation therapy, based on the 2017 Japanese guidelines for the management of community-acquired nonbacteremic pneumococcal pneumonia of the Japanese Respiratory Society (JRS). Setting Kobe university hospital, Japan. Methods A retrospective case series review including antibiotic use and length of hospital stay was conducted using the medical records from April 2008 to May 2019 at a university hospital in Japan. Main outcome measure Impact of antibiotic de-escalation therapy on the antibiotic costs. Results Among 55 patients who were eligible, the treating physicians de-escalated antibiotics in 28 (51%). The differences in the median length of hospital stay and the incidence of adverse drug reactions between the two groups were not statistically significant (p = 0.67 and 1.0, respectively). However, the median total antibiotic cost per infected patient in the de-escalated group was significantly lower than that in the non-de-escalated group [$269.8 ($195-$389) vs. $420.5 ($221-$799), p = 0.048]. Conclusion Antibiotic de-escalation based on the 2017 JRS guidelines leads to a reduction in total antibiotic costs for the management of community-acquired nonbacteremic pneumococcal pneumonia.

Efficacy of educational intervention on reducing the inappropriate use of oral third-generation cephalosporins.

PURPOSE: This study aimed to evaluate the efficacy of an educational intervention on reducing the inappropriate use of oral third-generation cephalosporins, the prevalence of resistant bacteria, and clinical outcomes. METHODS: A before-after study was conducted to compare the data for 1 year before and after intervention at a Japanese university hospital. Educational intervention included lectures for all medical staff on oral antibiotics and educational meetings with each medical department. The primary outcome was the use of oral third-generation cephalosporins in inpatients as measured by the monthly median days of therapy (DOTs) per 1000 patient days. Secondary outcomes included the use of each oral antibiotic in inpatients and outpatients, proportion of ß-lactamase-nonproducing ampicillin-resistant Haemophilus influenzae (BLNAR), penicillin-resistant Streptococcus pneumoniae (PRSP) and extended-spectrum ß-lactamase producing Escherichia coli (ESBLEC), the incidence of hospital-acquired Clostridioides difficile infection (HA-CDI), and hospital mortality. RESULTS: The use of oral third-generation cephalosporins in inpatients was significantly decreased after intervention [DOTs (interquartile range): 24.2 (23.5-25.1) vs. 3.7 (0.0-7.1), P < 0.001], and the value in outpatients was also decreased significantly. The use of fluoroquinolones and macrolides did not increase after intervention. The proportion of BLNAR, PRSP and ESBLEC did not change significantly during the study period. The incidence of HA-CDI was significantly decreased, and hospital mortality did not change after intervention. CONCLUSION: Educational intervention was effective in reducing the use of oral third-generation cephalosporins without increasing the use of broad-spectrum antibiotics and worsening clinical outcome. The prevalence of resistant bacteria did not change during the study period.

Pulmonary melanocytic nevus - A case report with a mutation analysis of common driver oncogenes.

Nevi are benign melanocytic tumors, and some nevi are considered to develop into malignant melanomas. Most nevi arise in the skin, but nevi occasionally occur in the conjunctiva, esophageal mucosa, or at other sites. Pulmonary melanocytic nevi are extremely rare, and only one case has been reported in the literature. Here, we present a case of pulmonary melanocytic nevus, involving a BRAF gene mutation (V600E), and we discuss the potential significance of this condition as a precursor to pulmonary malignant melanoma.

Unique expression profiles of mucin proteins in interstitial pneumonia-associated lung adenocarcinomas.

In order to clarify idiopathic interstitial pneumonia (IIP)-associated lung adenocarcinoma (LADC), we herein focused on the expression profiles of mucin proteins, the most common cellular differentiation markers. The expression of the mucin (MUC) 1, MUC2, MUC3B, MUC4, MUC5AC, MUC5B, MUC6, MUC7, MUC9, and MUC21 proteins was examined immunohistochemically and their levels were semi-quantified in 80 IIP-associated LADCs and 106 non-IIP LADCs. LADCs were divided into low and high expressers based on thresholds obtained from the receiver operating characteristic (ROC) curves of each mucin protein. Low expressers of MUC1, MUC7, and MUC21 and high expressers of MUC4, MUC5AC, MUC5B, and MUC9 were dominant in the IIP group. Multivariate analyses confirmed that the correlations between mucin expression profiles and IIP-associated LADCs were independent of putative confounding factors, such as smoking, gender, histological types, and cytological types. Thus, the expression profiles of these mucin proteins significantly differed between the IIP and non-IIP groups. IIP-associated LADCs appear to have unique cellular differentiation features and they may develop through a distinct histogenetic pathway. This is the first study to demonstrate that IIP-associated LADCs have unique mucin expression profiles.

Specific expression of MUC21 in micropapillary elements of lung adenocarcinomas - Implications for the progression of EGFR-mutated lung adenocarcinomas.

We investigated the significance of MUC21 in EGFR-mutated lung adenocarcinoma (LADC). Two-hundred forty-one surgically resected LADCs (116 EGFR-mutated and 125 wild-type tumors) were examined for immunohistochemical expression of MUC21 protein. A polyclonal antibody and two monoclonal antibodies (heM21C and heM21D) that bind differentially glycosylated MUC21 epitopes were used, and MUC21 proteins detected by these antibodies were named MUC21P, MUC21C, and MUC21D, respectively. MUC21 mRNA levels were semi-quantified and classified into "high" and "low". Among the immunohistochemical expression detected by three different antibodies, high expressors tended to be related to EGFR mutations. The three varieties of the immunohistochemical expressions were related to different histological elements in the EGFR-mutated LADCs. Either MUC21P or MUC21C high expressors had a higher proportion of lepidic elements with low papillary structure and micropapillary elements. MUC21D high expressors had a significantly higher proportion of micropapillary elements (Mann-Whitney test P ≤0.0001). Furthermore, MUC21D high expressors showed high incidence of lymphatic canal invasion and lymph node metastasis (Pearson x2 test, P = 0.0021, P = 0.0125), and a significantly higher recurrence rate (5-year recurrence-free survival 50.7% vs. 73.8%, log-rank test P = 0.0495). MUC21 proteins with a specific glycosylation status may be involved in the progression of EGFR-mutated LADCs, particularly at the stage where tumors are transforming from pure lepidic to micropapillary through low papillary lepidic lesions.

A subpopulation of airway epithelial cells that express hepatocyte nuclear factor 4α - its implication in the development of non-terminal respiratory unit-type lung adenocarcinoma.

A normal counterpart and precancerous lesion that non-terminal respiratory unit (TRU) lung adenocarcinomas (LADCs) develop from have not been clarified. Non-TRU LADCs specifically express hepatocyte nuclear factor 4α (HNF4α). Thus, we have been interested in airway epithelial cells that express HNF4α as the potential precursor of non-TRU LADC. The purposes of the present study are to report the frequency and distribution of HNF4α-expressing cells at the different airway levels, and to investigate the potential significance of the expression of HNF4α in the histogenesis of non-TRU LADC with a special reference to the relationship to bronchiolar metaplasia in idiopathic interstitial pneumonia. We herein identified a minor subpopulation of epithelial cells that express HNF4α in a physiological state. This subpopulation was mainly located in the terminal bronchioles and had the appearance of ciliated cells, which were mutually exclusive from Clara cells and others that strongly expressed thyroid transcription factor 1. Furthermore, the expression of HNF4α was similar in bronchiolar metaplastic lesions and the terminal bronchioles, and some of the metaplastic lesions showed an unequivocally higher frequency and expression level of HNF4α, which was comparable to non-TRU LADC. In summary, this is the first study to describe a subpopulation of ciliated cells that express HNF4α as a potential normal counterpart for non-TRU LADCs and suggests that bronchiolar metaplastic lesions that strongly express HNF4α are a precancerous lesion for non-TRU LADCs.

Acquisition of antimicrobial-resistant variants in repeated infections caused by Pseudomonas aeruginosa revealed by whole genome sequencing.

Pseudomonas aeruginosa, responsible for serious nosocomial-acquired infections, possesses intrinsic antibiotic resistance mechanisms and commonly exhibits multidrug resistance. Here, we report the evolving resistance profiles of strains isolated from the sputum of a patient being treated for repeated P. aeruginosa infections following cancer resection. Whole genome sequencing of six isolates obtained over a 2-month period revealed two key single nucleotide polymorphisms in the mexR and gyrB genes that affected efflux pump expression and antimicrobial resistance.

Bacteremia complicating urinary tract infection by Pseudomonas aeruginosa: Mortality risk factors.

OBJECTIVES: To examine the clinical risk factors for death within 30 days of diagnosis of Pseudomonas aeruginosa-causing bacteremia after a urinary tract infection. METHODS: A total of 62 patients with Pseudomonas aeruginosa isolated from both urine and blood at the same episode from January 2009 to December 2016 were enrolled in the present study. We retrospectively investigated clinical risk factors for death by comparison between surviving patients and those who died within 30 days after diagnosis of P. aeruginosa bacteremia. The comparison for risk factors for bacteremia-related death included 31 categories, such as age, laboratory data, underlying diseases, clinical history, history of surgery, care in the intensive care unit, P. aeruginosa susceptibility to the antibiotics used at the time of bacteremia diagnosis and consultation with urological department. RESULTS: The study included 48 men and 14 women aged 71.3 ± 10.4 years. Nine patients (14.5%) died of P. aeruginosa bacteremia. Statistical analysis showed that non-survivors had significantly lower albumin levels than survivors (2.07 ± 0.62 vs 2.62 ± 0.65; P = 0.023). The non-survivors had significantly higher rates of ventilator use, history of heart disease, septic shock and lower rates of consultation with urological departments after diagnosis (P < 0.05). CONCLUSIONS: Patients with bacteremia complicating urinary infection by P. aeruginosa have a low death rate. Earlier intervention by urologists might improve patients' outcome. Lower albumin levels, ventilator use, history of heart disease and septic shock are factors associated with higher mortality rate.

A molecular pathological study of four cases of ciliated muconodular papillary tumors of the lung.

Ciliated muconodular papillary tumors (CMPTs) are a recently categorized benign or low-grade malignant neoplasm that develops in the peripheral lung. Only about 40 cases have been reported to date, and the clinicopathological characteristics have yet to be defined in detail. Here, we present four cases of CMPTs with a focus on their immunohistochemical profiles and driver gene mutations. These tumors were a papillary proliferation of a mixture of ciliated, mucous, and basal cells located in the peripheral lung. Ciliated, mucous and basal cells were positive for TTF-1 when using the clone SPT24, but negative for HNF-4α. Basal cells were positive for p40. Mucous cells in some tumors were positive for MUC5AC and MUC6. The Ki-67 index was less than 5%, and strong expression of p53 was not detected. Three of the four tumors had a BRAF (V600E) driver mutation, an EGFR (del E746-T751/S752V) driver mutation, or driver mutations in both EGFR (E709G) and KRAS (G12V). These mutation types are rare for any histological type of lung cancer. The present results confirmed that CMPT is a neoplasm with immunohistochemical features and driver gene mutations that are distinct from those of common lung tumors.

Long-term efficacy of comprehensive multidisciplinary antibiotic stewardship programs centered on weekly prospective audit and feedback.

OBJECTIVE: To evaluate the long-term effects of comprehensive antibiotic stewardship programs (ASPs) on antibiotic use, antimicrobial-resistant bacteria, and clinical outcomes. DESIGN: Before-after study. SETTING: National university hospital with 934 beds. INTERVENTION: Implementation in March 2010 of a comprehensive ASPs including, among other strategies, weekly prospective audit and feedback with multidisciplinary collaboration. METHODS: The primary outcome was the use of antipseudomonal antibiotics as measured by the monthly mean days of therapy per 1000 patient days each year. Secondary outcomes included overall antibiotic use and that of each antibiotic class, susceptibility of Pseudomonas aeruginosa, the proportion of patients isolated methicillin-resistant Staphylococcus aureus (MRSA) among all patients isolated S. aureus, the incidence of MRSA, and the 30-day mortality attributable to bacteremia. RESULTS: The mean monthly use of antipseudomonal antibiotics significantly decreased in 2011 and after as compared with 2009. Susceptibility to levofloxacin was significantly increased from 2009 to 2016 (P = 0.01 for trend). Its susceptibility to other antibiotics remained over 84% and did not change significantly during the study period. The proportion of patients isolated MRSA and the incidence of MRSA decreased significantly from 2009 to 2016 (P < 0.001 and = 0.02 for trend, respectively). There were no significant changes in the 30-day mortality attributable to bacteremia during the study period (P = 0.57 for trend). CONCLUSION: The comprehensive ASPs had long-term efficacy for reducing the use of the targeted broad-spectrum antibiotics, maintaining the antibiotic susceptibility of P. aeruginosa, and decreasing the prevalence of MRSA, without adversely affecting clinical outcome.

[A case of micafungin-hyposensitive Candida glabrata due to FKS2 gene mutation].

Candida glabrata was continuously isolated in cultured urine samples from a subject with thrombotic thrombocytopenic purpura. Yeast-like fungal phagocytosis found in gram staining led to agents being tested for antifungal susceptibility, revealing hyposensitivity to micafungin (MCFG) of MIC < 2 mg/mL. MCFG administered for 10 days failed to cure C. glabrata infection. To clarify why hyposensitivity occurred, we analyzed the FKS gene sequence using the PCR, finding a deficit of 3 bases coding phenylalanine at FKS2 gene amino acid 659. MCFG hyposensitivity may thus occur in long-term candin-class anti-fungal agent treatment. Candin-class agents have potent anti-fungal activity with fewer adverse effects and are widely used clinically. Hyposensitivity due to resistant C. glabrata species showed thus be considered in fungal infection treatment.

Epidemiology of Escherichia coli, Klebsiella species, and Proteus mirabilis strains producing extended-spectrum ß-lactamases from clinical samples in the Kinki Region of Japan.

In the present study, nonduplicate, clinical isolates of extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli, Klebsiella spp, and Proteus mirabilis were collected during a 10-year period from 2000 to 2009 at several hospitals in the Kinki region, Japan. The detection rate of E coli markedly increased from 0.24% to 7.25%. The detection rate of Klebsiella pneumoniae increased from 0% to 2.44% and that of P mirabilis from 6.97% to 12.85%. The most frequently detected genotypes were the CTX-M9 group for E coli, the CTX-M2 group for K pneumoniae, and the CTX-M2 group for P mirabilis. E coli clone O25:H4-ST131 producing CTX-M-15, which is spreading worldwide, was first detected in 2007. The most common replicon type of E coli was the IncF type, particularly FIB, detected in 466 strains (69.7%). Of the K pneumoniae strains, 47 (55.3%) were of the IncN type; 77 P mirabilis strains (96.3%) were of the IncT type. In the future, the surveillance of various resistant bacteria, mainly ESBL-producing Enterobacteriaceae, should be expanded to prevent their spread.

Receptor activator of NF-κB ligand-dependent expression of caveolin-1 in osteoclast precursors, and high dependency of osteoclastogenesis on exogenous lipoprotein.

Although extensive studies have done much to clarify the molecular mechanisms of osteoclastogenesis during the last ten years, there may still be unknown molecules associated with osteoclast differentiation. Thus, we used fluorescent differential display to screen for genes whose expression is induced by receptor activator of NF-κB ligand (RANKL), a crucial molecule for osteoclast formation. We identified caveolin-1 (Cav-1) as a RANKL-induced gene. Cav-1 is a major structural protein of caveolae and lipid rafts, cholesterol-enriched microdomains in the plasma membrane (PM). The RANKL-induced Cav-1 was immediately conveyed to lipid rafts. Conversely, expression of flotillin-1 (Flot-1), another scaffolding protein of lipid rafts, was reduced during osteoclastogenesis, indicating conversion of Flot-1-predominant rafts into Cav-1-enriched rafts. However, in vitro osteoclastogenesis of precursor cells from Cav-1-null mice was comparable to that of wild-type mice, while Cav-2 expression in the knockout osteoclasts was maintained. Conversely, Cav-2 gene silencing in Cav-1-null osteoclast precursors using siRNA for Cav-2 increased osteoclast formation, suggesting that the Cav-1/Cav-2 complex may act as a negative regulator for osteoclastogenesis. On the other hand, destruction of lipid rafts by removal of cholesterol from the PM by methyl-ß-cyclodextrin (MCD) treatment caused disordered signal transductions for osteoclastogenesis, such as hyperactivation of Erk1/2 and insensitivity of Akt to RANKL stimulus. The abnormal signaling was reproduced by deleting exogenous lipoproteins from the culture medium, which also resulted in reduced osteoclast formation. In addition, the deletion caused delayed expression of nuclear factor of activated T cells c1 (NFATc1), and depressed its activation in the cytosol and inhibited its translocation into nuclei. Simultaneously, the deletion reduced the level of FcRγ, a trigger protein for initiating the calcium signaling needed to activate NFATc1, and decreased Cav-1 in lipid rafts. These findings indicate that the molecular mechanisms of osteoclastogenesis are highly dependent on extracellular lipoprotein and the integrity of lipid rafts, and suggest possible involvement of cholesterol.

[A case of micafungin-hyposensitive Candida glabrata due to FKS2 gene mutation].

Candida glabrata was continuously isolated in cultured urine samples from a subject with thrombotic thrombocytopenic purpura. Yeast-like fungal phagocytosis found in gram staining led to agents being tested for antifungal susceptibility, revealing hyposensitivity to micafungin (MCFG) of MIC <2 mg/mL. MCFG administered for 10 days failed to cure C. glabrata infection. To clarify why hyposensitivity occurred, we analyzed the FKS gene sequence using the PCR, finding a deficit of 3 bases coding phenylalanine at FKS2 gene amino acid 659. MCFG hyposensitivity may thus occur in long-term candin-class anti-fungal agent treatment. Candin-class agents have potent anti-fungal activity with fewer adverse effects and are widely used clinically. Hyposensitivity due to resistant C. glabrata species showed thus be considered in fungal infection treatment.

[Macrolide resistance and detection in Mycoplasma pneumoniae at Kansai Medical University Hirakata Hospital].

Mycoplasma pneumoniae causes bronchitis and pneumonia predominantly in subjects 5 to 20 years old. M. pneumoniae is detected by measuring specific antibodies and/or isolating the microorganism, but the frequency of false-positive/negative results, and the culture time required until isolation pose problems. We detected M. pneumoniae using real-time PCR with clinical specimens. We also determined the drug sensitivity of isolated M. pneumoniae and searched for the gene mutation responsible for macrolide resistance. In 275 cases of suspected M. pneumoniae infection, positive cases in real-time PCR numbered 40 (14.5%). Of these, 16 showed positive culture (5.8%). Of these 16, A2063G point mutation that causes macrolide resistance was found in 12. Drug sensitivity testing showed resistance to clarithromycin (MIC> or =64 microg/ml) in 11 and susceptibility in 4 (MIC 0.0039 microg/ml). The clarithromycin resistance ratio was 75%. Growth was insufficient for testing in 1 case. M. pneumoniae was susceptible to minocycline and all quinolone drugs. M. pneumoniae detection using real-time PCR proved much more sensitive than conventional culture. Macrolide resistance results correlated well with genomic mutation. Our study's macrolide resistance ratio was high at 75% possibly due to a restricted subject population that had been administered macrolide drugs elsewhere but with an unsatisfactory outcome. The increasing number of reports on macrolide resistance requires that we monitor drug resistance trends, particularly among macrolide derivatives.

T cells specific to hapten carrier but not to carrier alone assist in the production of anti-hapten and anti-carrier antibodies.

We examined the immune response of Balb/c mice to antigens prepared by conjugating 2-phenyloxazolone (phOx) to a foreign protein, ovalbumin (OVA), or a self-protein, mouse serum albumin (MSA), in order to study how these chemical modifications would affect immune recognition. We found that anti-OVA antibodies and CD4(+) T cells produced by OVA immunization reacted with OVA as well as with phOx-OVA. Anti-phOx antibodies were produced by phOx-OVA immunization and, interestingly, T cells from these mice reacted only with phOx-OVA but not with the intact OVA. These results suggested that the classical model of hapten-carrier immunization, in which B cells specific to hapten are activated with assistance from T cells specific to a carrier protein, might not be a major route for production of anti-hapten antibodies in hapten-carrier immunization. Furthermore, phOx-MSA immunization induced production of anti-phOx antibodies, which could not be accounted for in terms of the assistance of carrier-specific T cells because of the absence of MSA-specific T cells. Therefore, we proposed a new model in which anti-hapten B cells are assisted by T cells specific to the haptenated carrier.