Lymphoid and non-lymphoid tumors in E kappa-myc transgenic rabbits.

We developed transgenic rabbits with a DNA construct containing the proto-oncogene c-myc conjugated to the Ig kappa-chain enhancer gene, E kappa. One of four transgenic rabbits was mated to a normal rabbit and we used the offspring to develop a colony of rabbits carrying the E kappa-myc transgene in their germline. Of a total of 19 E kappa-myc transgenic rabbits, eight developed tumors. The tumors were characterized histologically and four were diagnosed as lymphoma, and one each was diagnosed as embryonic carcinoma, hepatoma, ovarian carcinoma and basal cell carcinoma. By Southern analysis, we showed the four lymphomas were of B-lymphoid lineage and by nucleotide sequence analysis we found three of them most likely used VH1 in their VDJ gene rearrangements. Cells from the embryonic carcinoma, the hepatoma and two of the B-lymphomas were adapted to tissue culture. We discuss the possibility that tumors of non-lymphoid origin develop in the E kappa-myc transgenic rabbits because of the potential for NF-kappa B to activate the kappa-enhancer in cells other than B-lymphoid lineage cells.

Effects of temperature strategy during cardiopulmonary bypass on cerebral oxygen balance.

BACKGROUND: Cerebral injury is the most serious complication of cardiopulmonary perfusion (CPB). With the advent of warm heart surgery, the effect of temperature strategy during perfusion and its effect on cerebral oxygen balance needs further study. METHODS: Three groups of patients (n=8, each) undergoing coronary artery bypass graft (CABG) surgery were studied. Group H, M and N underwent CPB at 28 degrees C, 32 degrees C and normothermia (>36 degrees C), respectively. The extracorporeal circuit was primed with Hartmann's solution 2.5 l and flow of 1.8 l min(-1) m(-2) at 28 degrees C, and 2.4 1 min-1 m(-2) at 32 degrees C and normothermia. All patients had a 4F oximetry catheter (Opticath, Oximetrix, Abbott Laboratories) inserted in the right jugular bulb for continuous measurement of jugular venous oxygen saturation (sjvO2). Data was collected at six specific times: T1- within 5 min before initiation of CPB, T2 - within the first minute after CPB, T3 - during stable temperature on CPB (28 degrees C, 32 degrees C, >36 degrees C), T4 - during rewarming at 34 degrees C in groups H and M, 15 min before coming off CPB in group N, T5 - 15 min after CPB, T6 - skin closure. At each time mean arterial pressure (MAP) and sjvO2 were recorded. Arterial blood and jugular venous blood were sampled for measurement of arterial oxygen saturation (saO2) and jugular venous lactate (sjv(lactate)), respectively. RESULTS: SjvO2 values decreased at times T2, T3 and T4 when compared to baseline (p<0.05) but there were no significant group differences at any time. Cerebral arteriovenous oxygen saturation (a-jvO2) differences mirrored sjvO2 changes. Sjv(lactate) values increased from baseline following CPB but fell consistently with time - there were no significant group differences at each time point. SjvO2 and a-jvO2 values were not significantly correlated with sjv(lactate). CONCLUSION: During pump flows employed in this study, cerebral oxygen balance and perfusion appear unaffected by temperature.

Recovery following tonsillectomy a comparison between tramadol and morphine for analgesia.

BACKGROUND: The optimal method of intraoperative analgesia for adult tonsillectomy is uncertain. It is important that recovery should be rapid so that the airway is not compromised. Tramadol hydrochloride is an analgesic with mixed -mu and non-opioid activities which has less respiratory depression effects compared to morphine. PATIENTS AND METHODS: We compared the recovery characteristics of patients undergoing tonsillectomy after they were given either morphine or tramadol for intra-operative analgesia. Seventy-nine ASA (American Society of Anesthesiologists) I patients were randomised to receive either tramadol 1.5 mg/kg (n = 44) or morphine 0.1 mg/kg (n = 35). A standard propofol-desflurane based general anaesthetic technique was used. RESULTS: Patients given tramadol recovered faster compared to morphine as demonstrated by the earlier eye opening at reversal (mean +/- SD, 4.7 +/- 1.5 min versus 5.6 +/- 1.8 min, p = 0.04). There was also significantly less nausea and vomiting in the patients given tramadol as compared to those given morphine (6.8% versus 28.6%, p = 0.01). There were no other clinically important adverse effects in either group. CONCLUSION: We conclude that tramadol given for intra-operative analgesia during tonsillectomy results in faster recovery with significantly less nausea and vomiting in the early postoperative period.

Audit of changes in serum urea and electrolytes following peri-operative intravenous fluid therapy.

One thousand and eleven patients discharged from the postoperative recovery ward with intravenous infusions were reviewed in order to audit the extent of assessment of serum urea and electrolytes (U&Es) and the change in serum U&Es over the perioperative period. 69.7% had preoperative U&Es estimation, 42.5% had both a pre- and postoperative estimation and in 5%, only a postoperative estimate was undertaken. 12.2% of patients whose U&Es were measured had an abnormal preoperative serum potassium compared to 17.2% postoperatively (NS). Compared to a preoperative incidence of 13%, more patients (27.3%) had an abnormal postoperative serum sodium (p < 0.0001). There was a tendency towards postoperative hyponatraemia: 10.0% in the preoperative period compared to a postoperative 25.3% (p < 0.0001). More tests were performed in the elderly (83.9% in age > 65 years versus 69% in age 17-64-p < 0.0001) who were more likely to have electrolyte disturbances preoperative hypokalaemia (p < 0.05), postoperative hyperkalaemia (p < 0.05), postoperative hyponatraemia (p < 0.03) and raised serum urea, both pre- and postoperatively (p < 0.0001 and p < 0.0005 respectively). Patients undergoing intraabdominal procedures did not have significantly different peri-operative electrolyte abnormalities. Fewer tests were performed in emergency patients, who were hypokalaemic in the postoperative period compared to elective patients (p < 0.01). There was a higher incidence of preoperative hyponatraemia and raised serum urea in the emergency group (p < 0.001 and p < 0.0002 respectively). Neurosurgical emergencies often had a degree of preoperative hypokalaemia which persisted after surgery (p < 0.0001). Results indicate an increased risk of serum electrolyte abnormalities following peri-operative intravenous fluid therapy. However in the majority of patients, the magnitude of the change is not significant clinically.

Perioperative management of a patient with congenital myasthenia gravis for elective caesarean section.

Congenital disorders of neuromuscular transmission are commonly referred to as congenital myasthenia gravis because of their clinical similarity to the immune-mediated disease. Differentiation between the immune-mediated and congenital forms of the disease is important, because therapy established for the former may not be appropriate for patients with the latter presentation. The course of this rare neuromuscular disorder during pregnancy and its influence on anaesthesia remain largely unknown. We report on the case of a 32-year-old parturient suffering from congenital myasthenia gravis scheduled for elective caesarean section. The perioperative management of this patient who underwent the operation under spinal anaesthesia was reviewed. The effects of anaesthetic agents and techniques on the course of congenital myasthenic patients may need further review in the light of latest findings in the electrophysiology, genetic and therapeutic studies of this syndrome.

A survey of patients' knowledge of anaesthesia and perioperative care.

AIM: The present study was undertaken to assess patients' knowledge of anaesthesia and perioperative care as well as their perception of anaesthetics and their role. METHODOLOGY: A questionnaire survey of 23 items was developed and completed pre-operatively by 132 patients. Included in this study were 45 men and 87 women; 80% with at least secondary education with a mean age of 39.9 and 35.6 years, respectively. RESULTS: Results indicated that only 56.8% of patients understood that anaesthetists are doctors. There were significant misconceptions though in general, knowledge was good. Although all patients realised the importance of fasting, however only 74.2% of patients realised it meant limitation of both solids and liquids from a specified time. Pain was the major concern among the patients surveyed (39.4%), followed by fear of not waking up after surgery (18.9%). Twenty-one per cent of patients believed that postoperative pain was a necessary part of the healing process and 28% thought that pain was something that they had to put up with in the postoperative period. Only 23.5% correctly identified the anaesthetist as being responsible for analgesia in the recovery period. A majority (75.8%) wished to have more information about anaesthesia. CONCLUSION: When forthcoming surgery and anaesthesia are discussed, it is important that patients realise that they are being cared for by anaesthetists who are doctors and efforts must be taken to educate the profession and public on the anaesthetists' role in perioperative care. This should enhance the professional image of anaesthesia and more importantly, improve patient confidence and quality of care.

Combined high-frequency ventilation (CHFV) in the treatment of acute lung injury--a case report.

A 22-year-old man was admitted to a district general hospital with chest injuries, a ruptured spleen and limb fractures, sustained in a road traffic accident. After an emergency splenectomy, the patient developed unilateral pulmonary oedema with hypoxaemia which was resistant to both conventional controlled mechanical ventilation (CMV) and independent lung ventilation (ILV). He was transferred to a specialist cardiothoracic unit where high frequency jet ventilation (HFJV) also failed to achieve adequate oxygenation. Combined high frequency ventilation (CHFV), using high frequency pulses from a Bromsgrove Penlon Jet ventilator superimposed onto small tidal volumes from an Engstrom Erica improved oxygenation rapidly to allow decreases in inspired oxygen fraction (FiO2), peak airway pressure (PAWP) and positive end expiratory pressure (PEEP). Progressive weaning from ventilatory support was then possible over five days. CHFV is a valuable technique in the treatment of acute catastrophic lung injury and needs wider recognition.

Pericardial injury following severe sepsis from faecal peritonitis--a case report on the use of continuous cardiac output monitoring.

We report on a case of a 43-year-old man who developed reversible myocardial depression and pericarditis related to severe sepsis secondary to rectosigmoid colonic perforation. The management of this patient was aided by the use of a continuous thermodilution cardiac output catheter and monitor, recently introduced in clinical practice.

Fibre-optic aided bougie (FAB) for simulated difficult tracheal intubation.

INTRODUCTION: Difficult intubation remains a key problem and the value of the gum elastic bougie as a first approach is well recognised. MATERIALS AND METHODS: A fine fibre-optic endoscope (Rapiscope, Cook Critical Care) was used in 50 patients to verify placement of a custom-designed hollow plastic bougie prior to "rail-roading" a tracheal tube. Following induction and muscle relaxation, direct laryngoscopy was performed after two-minutes of assisted ventilation. The laryngoscope blade was lowered to simulate difficult intubation and the bougie passed behind the epiglottis. The position of the introducer bougie was then checked using the Rapiscope. Following correct bronchoscopic identification of the tracheobronchial anatomy, a tracheal tube was then "rail-roaded" following withdrawal of the scope. RESULTS: All patients were successfully intubated following identification of the bronchial tree by the Rapiscope: three on the second attempt and the rest on the first. Mean (SD, range) time to successful bronchoscopic confirmation of correct placement of the bougie was 38 s (9.1 s, 19 to 60 s). All bronchoscopic assisted intubation were subsequently confirmed by capnography after tracheal tube insertion. Mean (SD, range) time to successful intubation was 106 s (14 s, 52 to 132 s). CONCLUSION: The fibre-optic assisted bougie (FAB) offers a promising technique in patients who may be difficult to intubate but who can be ventilated. Further developments are required to achieve a faster intubation time but oxygenation may be achieved by jetting down the hollow bougie.

The predictive value of intraoperative ST-segment monitoring as a marker of myocardial injury.

AIM: To evaluate the usefulness of dynamic intraoperative ST-monitoring in high-risk patients comparing it to preoperative clinical assessment and concurrent biochemical markers of cardiac injury. MATERIALS AND METHODS: Twenty-three patients clinically assessed as being at high risk for perioperative cardiac complications were recruited into this prospective, observational study in a public hospital. All had serial ECGs, cardiac enzymes and troponin-T measurements. The sensitivity, specificity, positive and negative predictive value of ST-segment changes in terms of predicting cardiac complications were calculated. We investigated the relationship between ST changes and biochemical markers of ischaemia and the predictive value of nonspecific (ASA) and specific (Goldman) clinical scores for cardiac complications. RESULTS: When correlated with cardiac complications, ST-segment monitoring had sensitivity 45.4%, specificity 100%, positive predictive value 100% and negative predictive value 66.7%. The correlation with CK-MB and troponin T was sensitivity 16.7% and 25%, specificity 73.3% and 75%, positive predictive value 20% and 20%, and negative predictive value 68.8% and 80%, respectively. The percentage of patients with cardiac complications increased with poor Goldman and ASA clinical scores; 25%, 40%, 62.5% and 100% in Goldman risk index groups of 0-5, 6-12, 13-25 and > 25, respectively; and 33.3% and 52.6% in ASA II and ASA III, respectively. CONCLUSIONS: This study demonstrates the importance of the anaesthesiologist preoperative assessment of cardiac risk. The probability that a patient with significant ST-depression will develop subsequent cardiac complications is 100%, which reflects its usefulness in this high-risk pre-selected sample. However, the test has a low sensitivity (45.4%).

Remifentanil in the management of laparoscopic resection of phaeochromocytoma--case reports.

INTRODUCTION: The laparoscopic adrenalectomy approach to phaeochromocytoma surgery offers the opportunity to use new short-acting drugs to facilitate rapid recovery. CLINICAL PICTURE: We report on 2 cases who underwent laparoscopic resection of phaeochromocytoma. The first was a 40-year-old lady who had been started on phenoxybenzamine 20 mg bd, but developed a recurrence of bronchial asthma after starting atenolol which was subsequently stopped. The second was a 51-year-old lady with neurofibromatosis who was taking phenoxybenzamine 20 mg bd and propanolol 20 mg tds. TREATMENT: The intraoperative management was facilitated by the stress suppressive effects of remifentanil infusion combined with nitroprusside as a vasodilator, and desflurane as an anaesthetic. OUTCOME: Both patients were extubated at the end of surgery and made uneventful recovery. CONCLUSION: Remifentanil possesses several useful properties, which deserve serious consideration in phaeochromocytoma surgery, particularly in the instance where beta-blockade is contraindicated. In combination with other titratable short-acting agents, it potentially facilitates rapid recovery especially following the laparoscopic approach to adrenalectomy.

Audit of total parenteral nutrition in an adult surgical intensive care.

INTRODUCTION: A preliminary one-year review of total parenteral nutrition (TPN) in the adult surgical intensive care unit (SICU) in view of its complications, cost and lack of consistent benefits in the critically ill. MATERIALS AND METHODS: All the case records of patients receiving TPN in the SICU starting from first January to end December 1998 were studied. RESULTS: Fifty patients received TPN during the study period. Four case records were unavailable. The indications for starting TPN were comparable with those set up by the Stanford University Hospital. Sepsis with gastrointestinal failure at 30.5% [95% CI, 17.7% to 45.8%] was one of the major indicators for TPN use and also the biggest contributor to mortality (50%) [95% CI, 35% to 65%]. Hyperglycaemia and line sepsis increased with duration of TPN use. Pneumonia, bacteraemia and wound infection peaked by the second week. Patients receiving TPN for inadequate and delayed enteral feeding fared better with 45.8% survival [95% CI, 30.9% to 61%]. None of the patients with polytrauma or malignancy cachexia died. 52.2% [95% CI, 37% to 67.1%] survived to be discharged from hospital. Caloric requirements were calculated using Harris-Benedect's equation and estimated using 30 to 35 kcal/kg/day. 64.3% were overfed and 50% received excessive non-protein calorie-to-nitrogen ratio. Ninety-eight per cent and 81% received less than the recommended amino-acid and glucose, respectively. Fifty-eight per cent received adequate lipids. CONCLUSION: This audit highlights the shortcomings in TPN prescription and characteristics of the attendant complications. Efforts must be directed towards encouraging uniformity and level of practice standards.

Comparison of the re-usable LMA Classic and two single-use laryngeal masks (LMA Unique and SoftSeal) in airway management by novice personnel.

In a single-blind randomized trial, three types of laryngeal masks: the reusable LMA Classic, the single-use LMA Unique and SoftSeal were inserted by novice medical officers in anaesthesia. Five successive attempts were undertaken with each mask type. The order of the mask type insertion was randomly selected. Mean (SD) insertion times for LMA Classic, LMA Unique and Soft Seal were 32.9 (12.3), 39.6 (23.4) and 49.4 (50.4) seconds respectively. Differences were only significant between LMA Classic and SoftSeal (P=0.012). There were no significant differences in first attempt success rates (LMA Classic 80%, LMA Unique 77% and SoftSeal 62%). The SoftSeal was most frequently associated with blood on the mask (32%) compared to the LMA Unique (9%) and LMA Classic (6%). Sore throat was experienced in 14% of patients in the LMA Unique group versus 41% and 42% in the LMA Classic and SoftSeal groups respectively. Mean +/- SD oropharyngeal leak pressure was significantly higher in the SoftSeal (21+/-6 cmH2O) compared to the LMA Classic (17+/-7 cmH2O) and LMA Unique (16+/-6 cmH2O). Novice medical doctors can be taught to insert disposable laryngeal masks. The SoftSeal took longer to insert, which resulted in a higher incidence of blood on the mask, but success rates did not differ The LMA Unique was associated with the lowest incidence of sore throat in the immediate postoperative period. A higher oropharyngeal leak pressure with the SoftSeal may indicate improved airway seal and protection against aspiration.

Maintenance of body temperature in elderly patients who have joint replacement surgery. A comparison between the heat and moisture exchanger and heated humidifier.

The effect of a heat and moisture exchanger on intra-operative aural canal (core) and mean skin temperatures was investigated in elderly patients who had elective total hip arthroplasty under general anaesthesia with artificial ventilation of the lungs. Group 1 (n = 20) did not receive any form of artificial humidification while in group 2 (n = 20) a heat and moisture exchanger was inserted in the breathing system and in group 3 (n = 20) the inspired gases were humidified and warmed at 40 degrees C by means of a heated humidifier. Time of surgery, intravenous fluid administration and operating theatre temperature were standardised. Mean (SD) aural canal (core) temperature decreased significantly in groups 1 and 2 (p less than 0.001), while there was a fall of 0.3 degrees C (0.6) in group 3, which was not significant. Mean skin temperature decreased during anaesthesia and surgery in both groups 1 and 2 (p less than 0.05), while it increased in group 3. There was a significantly greater loss of body heat in groups 1 and 2 compared with group 3 intra-operatively (p less than 0.001). We conclude tha a heat and moisture exchanger did not prevent the decrease in intra-operative body temperature in elderly patients.

Differential expression of 13 IgA-heavy chain genes in rabbit lymphoid tissues.

Molecular cloning techniques have recently demonstrated that rabbit has 13 different IgA C alpha H chain genes. This is in contrast to human and mouse that have only two and one C alpha heavy chain genes, respectively. In previous studies, nucleotide sequence analysis indicated that the 13 rabbit C alpha genes were potentially functional, and in vitro expression experiments showed that at least 12 of these genes were expressible. To understand the role of these multiple IgA isotypes we analyzed RNA of various lymphoid tissues for the presence of mRNA representing each of the multiple C alpha genes. We used the RNase protection assay with probes that are specific for the 13 different C alpha genes and we consistently found that at least 10 of the C alpha genes are expressed, albeit at different levels, in gut (small intestines), appendix, mesenteric lymph node, and mammary tissue. However, in salivary gland (submandibular), only seven of these genes are expressed at significant levels and in lung and tonsil only one C alpha gene, C alpha 4, is expressed at a level comparable to its expression in other tissues. Analysis of RNA of Peyer's patch showed differences in the level of C alpha gene expression between different animals and between different Peyer's patches of the same rabbit; in some cases, most of the C alpha genes were expressed, but in some cases only C alpha 4 was expressed at a significant level. Inasmuch as C alpha 4 is the 5' most C alpha gene we propose that IgA-producing cells are derived from B cells that have initially undergone isotype switching to C alpha 4 and we discuss various mechanisms that could explain switching to the more 3' C alpha genes.

Clonidine in the treatment of alcohol withdrawal in the intensive care unit.

We present two cases of patients with a past history of alcohol abuse admitted to the Intensive Care Unit (ICU) for treatment of respiratory problems, after multiple trauma and after sub-total colectomy, respectively. In both patients, features of alcohol withdrawal were prominent after sedation had been discontinued. Both were treated successfully with an infusion of clonidine.

In vitro induction of the expression of multiple IgA isotype genes in rabbit B cells by TGF-beta and IL-2.

The rabbit genome has 13 different Calpha genes that are expressed at different levels in mucosal tissues. To analyze the factors involved in the differential expression of these Calpha genes, we cloned and sequenced the promoters of the Ialpha regions that control the expression of sterile mRNA. We found that all Calpha genes, including Calpha3 and Calpha8, which are not expressed, and Calpha4, which is expressed at high levels, have similar nucleotide sequences in the Ialpha region, and all contain the recognition elements for TGF-beta in the promoter. B lymphocytes from popliteal lymph nodes or Peyer's patch activated in vitro could be induced by TGF-beta to express sterile IgA transcripts of all IgA isotypes, except Calpha2, Calpha3, and Calpha8. Many single B lymphocytes transcribed sterile mRNA of more than one IgA isotype, which demonstrates that transcription of sterile mRNA alone does not regulate the IgA isotype switch. The addition of IL-2 led to the expression of transcripts of mature IgA of all isotypes, except Calpha2, Calpha3, and Calpha8. The predominantly expressed isotype in these experiments was Calpha4. With the use of an IgA4-specific mAb we found that IgA4+ plasma cells are unevenly distributed throughout the small intestine such that many of the IgA+ plasma cells in the duodenum-jejunum produced IgA4, whereas in the lower part of the ileum IgA4-producing cells were almost absent. Because the microbial flora varies throughout the intestine, we suggest that the microbial flora creates different local environments and thus affects either isotype switching or homing of IgA-expressing cells.

Preferential VH gene usage in rabbit Ig-secreting heterohybridomas.

B cells from leukemic rabbits preferentially use a single VH gene, VH1, in their VDJ gene rearrangements. To determine whether Ig-secreting B cells from normal rabbits also preferentially use VH1, we generated rabbit X mouse heterohybridomas that stably secreted rabbit Ig that expressed VHa allotypic specificities and analyzed the VH genes used in their VDJ gene rearrangements. We cloned the VDJ genes from nine heterohybridomas, and by comparing the restriction map of the DNA immediately 5' of the translational start site of these VDJ genes to that of the same region 5' of VH1, we showed that eight of the nine heterohybridoma clones use VH1. Comparison of the nucleotide sequences of the eight VH1-using VDJ genes with the nucleotide sequence of germ-line VH1 showed that each of them had somatically diversified. The diversified regions included clustered nucleotide changes and codon insertions and deletions, such as would be expected if the diversification process involved somatic gene conversion. We searched our database of germ-line VH genes for genes that could serve as donors for the gene conversion events, and we identified potential VH donor genes for five regions of diversification. One of these regions of diversification spanned at least 132 bp and included a codon insertion as well as 15 nucleotide changes. The data confirm that Ab diversity may be generated by a somatic gene conversion-like mechanism. The results directly demonstrate that Ig-secreting B cells from normal rabbits preferentially use VH1 in their VDJ gene rearrangements.

Effect of weaning on oxygen consumption and cardiovascular function. A comparison of continuous flow and demand valve systems.

This study compared the continuous positive airways pressure mode of the demand valve system of the Engstrom Erica ventilator with a custom-made continuous flow continuous positive airways pressure system in terms of the oxygen cost of breathing during weaning from mechanical ventilation. Ten consecutive patients in our intensive care unit, with thermodilution pulmonary artery flotation catheters in situ, were studied. Measurements were carried out under steady-state conditions, initially when breathing spontaneously with continuous positive airways pressure via the Erica and then when transition to the continuous flow system was achieved. There were no significant differences between the two methods of providing continuous positive airways pressure in terms of the measured and derived physiological variables studied, with the exception of oxygen consumption. Oxygen consumption with the continuous flow system was significantly less than with the Erica (142.8 (SEM 31.4) ml.min-1.m-2 compared with 165.8 (SEM 30.5) ml.min-1.m-2, p < 0.05). This difference reflects the reduced oxygen cost of breathing when the custom-made continuous flow system was used during weaning.

Rabbit major histocompatibility complex. IV. Expression of major histocompatibility complex class II genes.

The rabbit MHC class II DP, DQ, and DR alpha and beta chain genes were transfected into murine B lymphoma cells. The transfected cells expressed R-DQ and R-DR molecules on the cell surface but they did not express the R-DP genes either on the cell surface or at the level of mRNA. Northern blot analyses showed that the R-DP genes were expressed, albeit at low levels, in rabbit spleen. Similar analyses showed that the R-DQ and R-DR genes were expressed at high levels in rabbit spleen. A new monoclonal anti-rabbit class II antibody, RDR34, has been developed and shown to react with the R-DR transfected cells and not with the R-DQ transfected cells. The previously described monoclonal anti-rabbit class II antibody, 2C4, reacted with the R-DQ transfected cells and not with the R-DR transfected cells. Thus, 2C4 and RDR34 MAb's are specific for the R-DQ and R-DR molecules, respectively. Each of the antibodies reacted with approximately 50% of rabbit spleen cells as shown by immunofluorescent antibody studies.