The tumour-suppressor genes lgl and dlg regulate basal protein targeting in Drosophila neuroblasts

Drosophila neuroblasts are a model system for studying asymmetric cell division: they divide unequally to produce an apical neuroblast and a basal ganglion mother cell that differ in size, mitotic activity and developmental potential. During neuroblast mitosis, an apical protein complex orients the mitotic spindle and targets determinants of cell fate to the basal cortex, but the mechanism of each process is unknown. Here we show that the tumour-suppressor genes lethal giant larvae (lgl) and discs large (dlg) regulate basal protein targeting, but not apical complex formation or spindle orientation, in both embryonic and larval neuroblasts. Dlg protein is apically enriched and is required for maintaining cortical localization of Lgl protein. Basal protein targeting requires microfilament and myosin function, yet the lgl phenotype is strongly suppressed by reducing levels of myosin II. We conclude that Dlg and Lgl promote, and myosin II inhibits, actomyosin-dependent basal protein targeting in neuroblasts.

Unplanned admissions following outpatient otologic surgery: the University of Arkansas experience

We analyzed the outpatient otologic surgery experience at our institution to identify those factors that are associated with a high risk of postoperative complications that require an unplanned hospital admission. We found that among a group of 662 patients who underwent group II otologic procedures (i.e., tympanoplasty with or without mastoidectomy, stapedotomy, and middle ear exploration), the overall admission rate was 4.7%, of which 3.9% were unplanned. A significantly larger percentage of children were admitted than adults (5.7 vs. 2.3%), primarily for nausea and vomiting. Three factors were significantly associated with unplanned admissions: the type of surgery (tympanomastoidectomy with ossicular reconstruction), the duration of general anesthesia (> 2 hr), and asthma as a coexisting condition. The choice of antiemetic administered (ondansetron or droperidol) and the specific agents used for general anesthesia did not appear to have any significant impact on unplanned admissions. We recommend that the three predisposing factors be taken into consideration when formulating the treatment plan. Scheduling an inpatient procedure for patients who have risk factors for complications requiring hospitalization would avoid the extra costs and stress associated with unplanned admissions.

Prospero distinguishes sibling cell fate without asymmetric localization in the Drosophila adult external sense organ lineage

The adult external sense organ precursor (SOP) lineage is a model system for studying asymmetric cell division. Adult SOPs divide asymmetrically to produce IIa and IIb daughter cells; IIa generates the external socket (tormogen) and hair (trichogen) cells, while IIb generates the internal neuron and sheath (thecogen) cells. Here we investigate the expression and function of prospero in the adult SOP lineage. Although Prospero is asymmetrically localized in embryonic SOP lineage, this is not observed in the adult SOP lineage: Prospero is first detected in the IIb nucleus and, during IIb division, it is cytoplasmic and inherited by both neuron and sheath cells. Subsequently, Prospero is downregulated in the neuron but maintained in the sheath cell. Loss of prospero function leads to ‘double bristle’ sense organs (reflecting a IIb-to-IIa transformation) or ‘single bristle’ sense organs with abnormal neuronal differentiation (reflecting defective IIb development). Conversely, ectopic prospero expression results in duplicate neurons and sheath cells and a complete absence of hair/socket cells (reflecting a IIa-to-IIb transformation). We conclude that (1) despite the absence of asymmetric protein localization, prospero expression is restricted to the IIb cell but not its IIa sibling, (2) prospero promotes IIb cell fate and inhibits IIa cell fate, and (3) prospero is required for proper axon and dendrite morphology of the neuron derived from the IIb cell. Thus, prospero plays a fundamental role in establishing binary IIa/IIb sibling cell fates without being asymmetrically localized during SOP division. Finally, in contrast to previous studies, we find that the IIb cell divides prior to the IIa cell in the SOP lineage.

Use of intravascular ultrasound improves long-term clinical outcome in the endovascular management of atherosclerotic aortoiliac occlusive disease

PURPOSE

This study was undertaken to determine whether the use of intravascular ultrasound (IVUS) during balloon angioplasty and stenting of atherosclerotic aortoiliac occlusive lesions improved long-term clinical outcome. IVUS has been previously shown to be more accurate than arteriography in evaluating the deployment of stents in both peripheral and coronary arteries. Incomplete stent deployment has been anecdotally identified as a cause of restenosis or occlusion of a treated lesion. To our knowledge, there have been no previous studies that demonstrate whether the use of IVUS will affect the long-term patency rate of stented arterial lesions.

METHODS

Between March 1992 and October 1995, 52 patients with symptomatic aortoiliac occlusive disease underwent balloon angioplasty and stenting of their lesions. We retrospectively reviewed these cases to determine whether the use of IVUS influenced the long-term patency rate of these interventions. Follow-up ranged from 1 to 4 years with a mean of 28 months.

RESULTS

Fifty-two patients had confirmation of adequate stent deployment by arteriography. IVUS was used in conjunction with arteriography in 36 patients to evaluate stent deployment. Patients in the IVUS-assisted group were slightly younger than those patients who were evaluated solely by arteriography (p < 0.01). No statistical differences were noted between the two groups with respect to coronary artery disease, diabetes mellitus, obstructive pulmonary disease, hypertension, or obesity. Length of hospital stay, number of stents used, and preoperative ankle brachial indexes were comparable in both groups. In the arteriography plus IVUS group, 40% of patients had underdeployed stents by IVUS evaluation, though they appeared adequately expanded by arteriography. No restenoses or occlusions were seen in the arteriography plus IVUS group. Restenosis or occlusion of the stented lesion occurred in 25% of patients evaluated by arteriography alone (p < 0.01). These failures were treated by either thrombolysis or catheter thrombectomy and were then evaluated with IVUS. All were found to have underdeployed stents. Subsequent treatment consisted of adequate redeployment of existing stents using IVUS criteria. These salvaged reconstructions have continued to remain patent.

CONCLUSIONS

The use of IVUS may be the best means for assessing adequacy of arterial stent deployment. Our study suggests that the use of IVUS improves the long-term clinical outcome of balloon angioplasty and stented aortoiliac occlusive lesions.

Mobile atheroma of the aortic arch is an underestimated source of embolization

BACKGROUND

Mobile atheroma are associated with increased perioperative strokes in patients undergoing coronary artery bypass surgery. Peripheral embolization is an additional risk. Transesophageal echocardiography (TEE) accurately identifies mobile atheroma. Recent reports have discussed the possible influence of anticoagulant therapy in promoting peripheral cholesterol embolization.

METHODS

Fourteen patients with mobile atheroma were treated with anticoagulation. A review of literature reporting results and complications of anticoagulation in the treatment of this condition was compared with our recent experience.

RESULTS

Between 1994 and 1996, 14 patients with peripheral embolization and mobile atheroma confirmed by TEE were anticoagulated. Clinical follow-up between 6 to 30 months has demonstrated no further evidence of systemic embolization since anticoagulation. Furthermore, repeat TEE in 3 of 14 patients no longer visualized mobile atheroma.

CONCLUSIONS

Mobile atheroma are recognized sources for embolization. Patients with generalized atherosclerosis should be screened for this condition in cases of systemic embolization. Anticoagulation may have therapeutic considerations in the management of this condition.

IL-7 overexpression in transgenic mouse keratinocytes causes a lymphoproliferative skin disease dominated by intermediate TCR cells: evidence for a hierarchy in IL-7 responsiveness among cutaneous T cells

IL-7 is a keratinocyte-derived lymphocyte growth factor critical for the development of gammadelta T cells including murine dendritic epidermal T cells (DETC). We derived transgenic mice that overexpress IL-7 in basal keratinocytes under the control of the human K14 promoter. These K14/IL-7 mice develop dermal and epidermal T cell infiltrates associated with alopecia. This lymphoproliferative skin disease is substantially more severe in mice homozygous for the K14/IL-7 transgene. Conventional DETC expressing a Vgamma5 Vdelta1 TCR are rare or absent among the cutaneous T cells in these mice. The T cells in the skin infiltrates of young K14/IL-7 mice are predominantly gammadelta T cells that express intermediate levels of TCR, are negative for E-cadherin, often lack expression of CD2, and include cells that coexpress NK1.1. T cells expressing intermediate levels of a TCR-alphabeta are also present in transgenic skin, and progressively increase in number as the mice age. Phenotypically similar intermediate gammadelta and alphabeta T cell subsets also constitute the major lymphocyte populations recovered from organ culture of normal mouse skin in the presence of IL-7, suggesting that the T cells that accumulate in the epidermis of K14/IL-7 mice are derived from precursors normally resident in skin. We conclude that intermediate TCR cells, some of which coexpress NK1.1, can be selectively expanded in skin under the influence of IL-7 produced locally. Our results also suggest that features of the epidermal microenvironment besides keratinocyte-derived IL-7 account for the normal predominance of Vgamma5 Vdelta1 DETC in mouse epidermis.

IL-7 overexpression in transgenic mouse keratinocytes causes a lymphoproliferative skin disease dominated by intermediate TCR cells: evidence for a hierarchy in IL-7 responsiveness among cutaneous T cells

IL-7 is a keratinocyte-derived lymphocyte growth factor critical for the development of gammadelta T cells including murine dendritic epidermal T cells (DETC). We derived transgenic mice that overexpress IL-7 in basal keratinocytes under the control of the human K14 promoter. These K14/IL-7 mice develop dermal and epidermal T cell infiltrates associated with alopecia. This lymphoproliferative skin disease is substantially more severe in mice homozygous for the K14/IL-7 transgene. Conventional DETC expressing a Vgamma5 Vdelta1 TCR are rare or absent among the cutaneous T cells in these mice. The T cells in the skin infiltrates of young K14/IL-7 mice are predominantly gammadelta T cells that express intermediate levels of TCR, are negative for E-cadherin, often lack expression of CD2, and include cells that coexpress NK1.1. T cells expressing intermediate levels of a TCR-alphabeta are also present in transgenic skin, and progressively increase in number as the mice age. Phenotypically similar intermediate gammadelta and alphabeta T cell subsets also constitute the major lymphocyte populations recovered from organ culture of normal mouse skin in the presence of IL-7, suggesting that the T cells that accumulate in the epidermis of K14/IL-7 mice are derived from precursors normally resident in skin. We conclude that intermediate TCR cells, some of which coexpress NK1.1, can be selectively expanded in skin under the influence of IL-7 produced locally. Our results also suggest that features of the epidermal microenvironment besides keratinocyte-derived IL-7 account for the normal predominance of Vgamma5 Vdelta1 DETC in mouse epidermis.

Use of intravascular ultrasound in the endovascular management of atherosclerotic aortoiliac occlusive disease

BACKGROUND

Intravascular ultrasound (IVUS) has been described as interesting technology in search of a clinical application by some and by others as a valuable diagnostic tool for many endovascular interventions. Its clinical usefulness has yet to be fully defined. When used during endovascular interventions, it can provide structural and diagnostic information, assess effectiveness of the therapy, and identify treatment-related complications.

METHODS

Thirty-two consecutive patients with atherosclerotic aortoiliac occlusive disease who presented with 40 separate arterial lesions were evaluated with IVUS before and after balloon angioplasty and intraluminal stent placement. Information obtained from IVUS was compared with similar data obtained from simultaneous angiographic images. Both techniques were evaluated with respect to assessment of vessel size, lesion location, adequacy of therapy, and identification of complications.

RESULTS

Real time IVUS imaging compared with angiographic imaging showed that in 62% of the patients, vessel diameter was underassessed using angiographic criteria alone. More importantly, 40% (16 of the 40 lesions) had underdeployed stents by IVUS evaluation that appeared adequately expanded by angiographic criteria. Further stent expansion with a larger balloon was necessary to achieve accurate stent to vessel wall apposition. This was found to be significant by an exact binomial 95% confidence interval. Incomplete stent deployment has been identified as a possible cause for restenosis and vessel occlusion. Information obtained from IVUS imaging substantially altered the endovascular therapy in approximately 40% of our patients and provided valuable vessel sizing and lesion composition information in 62% of the patients.

CONCLUSION

Intravascular ultrasound can provide important diagnostic information that can alter the conduct of selected endovascular procedures. It is especially useful when the procedure requires deployment of arterial stents.

Two routes to naming: a case study

We report the case of an aphasic patient, KP, whose spontaneous speech and ability to communicate verbally were severely reduced. His comprehension of written words was preserved. Naming was relatively preserved for objects but impaired for actions. We designed experiments to investigate his verb processing and sentence completion. KP's knowledge of verb syntax was impaired in contrast to his relatively preserved knowledge of verb semantics. His ability to retrieve a noun on visual confrontation was significantly better than his ability to retrieve the same pool of nouns through propositional language. We interpret the data in terms of two 'routes' to noun-retrieval, a nominal route and a propositional speech route. Furthermore, we suggest that the dissociation between verb syntax and verb semantics can also be accounted for within this framework.

Constitutive expression of B7-1 (CD80) on mouse keratinocytes does not prevent development of chemically induced skin papillomas and carcinomas

Expression of the B7-1 (CD80) costimulatory molecule in a variety of tumor cell lines leads to an enhanced CD8+ T cell response to tumor Ags. We used transgenic mice constitutively expressing B7-1 on keratinocytes (K14/B7-1 line) to determine whether keratinocyte B7-1 expression would inhibit the development of papillomas and carcinomas following two-stage chemical carcinogenesis in skin. FVB inbred mice carrying the K14/B7-1 transgene and controls were initiated with 25 micrograms of 7,12-dimethylbenz[a]anthracene and promoted weekly with 5 micrograms of 12-O-tetradecanoylphorbol-13-acetate for 20 wk. Expression of the B7-1 transgene did not result in statistically significant decreases in the mean number of papillomas or carcinomas compared with controls. The incidence of carcinomas in both transgenic and control mice reached 90% or greater by 60 wk after initiation. Carcinoma cell lines established from the K14/B7-1 mice maintained expression of B7-1 and Kq. These B7-1 expressing carcinomas grew progressively following intradermal injection into syngeneic FVB mice, further demonstrating their inability to evoke protective tumor immunity. These same carcinoma cell lines were rapidly rejected by minor alloantigen-mismatched SWR mice, confirming their susceptibility to immune effector mechanisms. The failure of constitutive B7-1 expression on keratinocytes to prevent the growth of squamous cell papillomas and carcinomas may reflect the limited immunogenicity of tumors arising after initiation-promotion carcinogenesis. Our results in this transgenic model system are further evidence that B7-1 gene therapy alone may not be sufficient to induce protective immunity to some types of tumors.

Optic aphasia: a case with spared action naming and associated disorders

AG, a pure case of optic anomia (object naming impaired; action naming good) is described. We consider the fit of experimental data from AG to different theoretical accounts of optic aphasia. Overall, we find no evidence for impairments intrinsic to semantic representations, but we note a number of problems that we interpret as indicating a slight, and specific, weakness in semantic access from vision. We also note a mild problem in generating names to a cue (verbal fluency). The main aim of the report was to provide a full description of tests of visual, semantic, and speech output skills in this patient in relation to the processing of visually presented objects and scenes, within a sequential information processing account which enables some theoretical implications to be drawn, albeit not conclusively.

Constitutive expression of B7-1 (CD80) on mouse keratinocytes does not prevent development of chemically induced skin papillomas and carcinomas

Expression of the B7-1 (CD80) costimulatory molecule in a variety of tumor cell lines leads to an enhanced CD8+ T cell response to tumor Ags. We used transgenic mice constitutively expressing B7-1 on keratinocytes (K14/B7-1 line) to determine whether keratinocyte B7-1 expression would inhibit the development of papillomas and carcinomas following two-stage chemical carcinogenesis in skin. FVB inbred mice carrying the K14/B7-1 transgene and controls were initiated with 25 micrograms of 7,12-dimethylbenz[a]anthracene and promoted weekly with 5 micrograms of 12-O-tetradecanoylphorbol-13-acetate for 20 wk. Expression of the B7-1 transgene did not result in statistically significant decreases in the mean number of papillomas or carcinomas compared with controls. The incidence of carcinomas in both transgenic and control mice reached 90% or greater by 60 wk after initiation. Carcinoma cell lines established from the K14/B7-1 mice maintained expression of B7-1 and Kq. These B7-1 expressing carcinomas grew progressively following intradermal injection into syngeneic FVB mice, further demonstrating their inability to evoke protective tumor immunity. These same carcinoma cell lines were rapidly rejected by minor alloantigen-mismatched SWR mice, confirming their susceptibility to immune effector mechanisms. The failure of constitutive B7-1 expression on keratinocytes to prevent the growth of squamous cell papillomas and carcinomas may reflect the limited immunogenicity of tumors arising after initiation-promotion carcinogenesis. Our results in this transgenic model system are further evidence that B7-1 gene therapy alone may not be sufficient to induce protective immunity to some types of tumors.

Bioavailability of pseudoephedrine from controlled release formulations in the presence of guaifenesin in human volunteers

A multiple-dose bioequivalence study with six healthy human volunteers was conducted. The bioavailability of an experimental controlled release tablet containing pseudoephedrine was compared with a marketed controlled release pseudoephedrine capsule in a three-way crossover study. Plasma samples, collected serially after oral drug administration, were analyzed for pseudoephedrine content using a specific HPLC method with UV detection. The bioavailability parameters, area under the concentration-time curve (AUC), maximum plasma concentration Cmax, and time to peak (Tmax) were obtained from the plasma concentration-time data. Additionally, model independent pharmacokinetic parameters were estimated. Analysis of variance of the data revealed no statistically significant differences between the test and the reference formulation. The presence of guaifenesin in the sustained release tablet did not influence pseudoephedrine bioavailability. The relative bioavailability of the tablet dosage form with respect to the capsule was found to be 100.8%. Classical and Westlake 95% confidence limits as well as the two one-sided t test, proposed by Schuirmann, and the Anderson-Hauck power analysis supported the inference that the two formulations demonstrated comparable bioavailabilty, even in the presence of guaifenesin. Using a non-linear regression program, it was found that the pharmacokinetics of pseudoephedrine followed a simple one-compartment disposition model with no lag time. Additionally, an in vitro-in vivo correlation, based on the estimation of cumulative relative fraction absorbed, was developed between the absorption of pseudoephedrine in humans and the in vitro dissolution time.

Confabulations related to tacit awareness in visual neglect

The case of a man with left-sided visuospatial neglect is reported. His performance on a test for neglect, the "burning house test", is analysed and compared with that of other patients referred to in the literature. We suggest that the confabulations neglect patients may produce when confronted with this test reflect the degree of preconscious awareness for left-sided features.

Optic aphasia with spared action naming: a description and possible loci of impairment

A brief functional description is given of an optic aphasic patient, A.G., who shows a pure and isolated deficit in naming visually presented objects on confrontation, but with sparing of visual action names. We show how some tasks related to imagery are compromised in this patient and speculate on possible functional site(s) of impairment in terms of the routes from perception to naming. We suggest why action naming may be spared in such cases.

Hemispheric activation vs spatio-motor cueing in visual neglect: a case study

We report a case of mild visuo-spatial neglect consequent upon right-hemisphere stroke. At the time of testing, the patient had a complete left visual field deficit but only a very slight left hemiparesis. Under conventional testing conditions, line bisection performed with the right hand showed more severe left neglect than when performed with the left hand. This pattern of performance could, however, be modified, both quantitatively and qualitatively, by changing the starting position of the patient's hand when bisecting horizontal lines. The results suggest that spatio-motor cueing has a more profound effect upon task performance than does differential hemispheric activation per se. We also provide a demonstration that, in a normal subject, the starting position of the hand is likewise a crucial determinant of task performance. In this case, however, there is also an interaction between the hand (and hence hemisphere) deployed and the position of that hand in space.

Pharmacokinetics and protein binding of methocarbamol in renal insufficiency and normals

We determined plasma methocarbamol concentrations over 24 h following a 1.5 g methocarbamol dose (off-dialysis day) to 8 chronic haemodialysis patients and compared these results to those from 17 healthy male volunteers. The harmonic mean elimination half-life was similar between the two groups, 1.24 and 1.14 h, respectively. tmax and the weight-adjusted Cmax were 1.1 h and 27.0 mg.m-1 for haemodialysis patients and 1.1 and 23.1 mg.l-1 for normals. Relative systemic availability was assessed by comparing weight-normalized AUC x k10 products. These results indicate no significant differences with respect to methocarbamol absorption, with the relative systemic availability in patients being 113%. These data suggest that absorption and elimination of methocarbamol is similar between normal subjects and patients undergoing maintenance haemodialysis.

Individual variation in line bisection: a study of four patients with right hemisphere damage and normal controls

In a previous study of line bisection, [Manning et al., Neuropsychologia 28, 647-655, 1990] we have shown that normal young adults show significant linear regressions of both transection displacement (TD) and standard deviation (SD) on line length. Furthermore, there was considerable individual variation in the magnitude of SDs and the direction and magnitude of TDs. These two sources of variance were uncorrelated. In the current study we provide a constructive replication of these findings on an older population that constitutes a more appropriate control sample for patients with stroke. The performance of four patients with right hemisphere stroke is then interpreted in terms of the constraints observed in normal subjects. All the patients showed qualitatively intact line bisection, but with quantitative impairments of varied severity. When analysed in two pairs, the patients also showed a double-dissociation between the magnitude of their mean transection displacements and the SDs of those means. This result is in conformity with the prediction based upon a lack of correlation between these two measures in normal subjects.

Individual variation in line bisection: a study of normal subjects with application to the interpretation of visual neglect

Investigations of left visuo-spatial neglect are reviewed with special reference to line bisection performance. Attention is then drawn to inconsistencies in the direction and magnitude of transection displacements in group studies of normal controls. We argue that the lack of reliable information about normal mechanisms for line bisection makes it impossible to interpret pathological performance in neglect. Accordingly, we report a case-series of 22 normal young adults, each of whom bisects 10 lines of differing lengths 10 times each. There is very substantial between-subject variation in both the magnitude and direction of the linear regression of transection displacement on line length; there are likewise considerable differences in the magnitude of the linear regression of standard deviation on line length. These two sources of individual variation are uncorrelated. We propose a psychophysical theory of line bisection, and suggest that the basic mechanisms responsible for task-performance are qualitatively intact in visuo-spatial neglect, albeit quantitatively impaired.

Can parents do a throat culture?

Throat swabs for Group A beta-hemolytic Streptococcus were obtained from 98 patients, ages 4 to 17 years, both by their parents and by physician investigators. Compared with results obtained by physicians, there was a false negative rate of 32% (P less than 0.001) for the parents. The discrepancy was greater in the youngest age group (38% false negative rate in the 4- to 8-year-olds) compared with older children (P less than 0.001). The overall sensitivity and negative predictive value for the parent-obtained swabs were 68 and 45%, respectively. In the 4- to 8-year-old group, these values were 62 and 37%, respectively. Because there were no false positives the positive predictive value was 100%. We conclude that the false negative rate for untrained parents obtaining throat swabs is too high to warrant the implementation of home testing for Group A streptococci.

Sustained release of 5-fluorouracil from ethylene acetate copolymer

Pharmacologic inhibition of fibroblast proliferation and scar formation remains an important consideration in many ophthalmologic surgical procedures. Such inhibition is particularly important in glaucoma filtration surgery. A sustained release system for 5-fluorouracil (5-FU) using ethylene vinyl acetate copolymer (Elvax) was characterized in vitro. 5-FU was incorporated into Elvax discs of 4 mm diameter. Discs were coated to allow sustained and predictable release over a 14 day period. Alteration of coatings, which act as rate-controlling membranes, allowed variation in the pattern of 5-FU release from the core which acts as the drug reservoir. This system for the sustained release of 5-FU may prove valuable in glaucoma surgery where the suppression of cellular proliferation is desired. The non-inflammatory nature of Elvax suggests this compound may provide an alternative means of 5-FU delivery.

Interhemispheric asymmetry in facial expression recognition: relationship to field-dependence

Sixty college students, 30 males and 30 females, with a well defined cognitive style (measured by means of three tests), carried out a recognition task of six unambiguous facial expressions which were unilaterally presented in a tachistoscopic condition. A significant left visual field superiority was present for the field independenct subjects; a low but significant right visual field superiority was present for the field dependent subjects. No differences were found between the sexes.

Exclusive binding of immunoglobulin to Fc gamma receptors on macrophages in 3-methylcholanthrene-induced murine tumors

Immunogenic, chemically induced, murine tumors generally are infiltrated with large numbers of Fc gamma receptor (Fc gamma R)-positive cells, most of which are mononuclear phagocytes. This study demonstrates in inbred C3H/HeN mice that such immunogenic tumors contain large amounts of cell-bound immunoglobulin (Ig) and that, within the sensitivity limits of indirect immunofluorescence, the tumor-associated Ig is bound exclusively to host-derived Fc gamma R-positive cells. Depletion of Fc gamma R-positive cells from tumor cell suspensions removed all Ig-bearing cells. Specific competitive elution of the endogenous Ig with heterologous nonimmune IgG established that the endogenous Ig was bound through the Fc gamma R. Tumor-associated Fc gamma R-positive, Ig-bearing cells could be detected with soluble antigen-antibody complexes, and mononuclear phagocytes to which the exogenous complexes were bound expressed Fc gamma R at a level significantly above normal. The role of this macrophage-associated Ig in determining the level of interaction between host cells and the tumor remains to be determined.