Cytokine, catabolic enzyme and structural matrix gene expression in synovial fluid following intra-articular administration of triamcinolone acetonide in exercised horses.

REASON FOR PERFORMING STUDY: The frequent use of intra-articular triamcinolone acetonide (TA) in performance horses warrants further study of the duration of as well as the beneficial and detrimental effects on gene expression associated with administration. OBJECTIVES: To assess the effects of intra-articular administration of TA on the expression of selected anti- and proinflammatory and structural matrix genes following its administration into joints of exercised Thoroughbred horses and to correlate these effects with plasma and synovial fluid drug concentrations. STUDY DESIGN: Block design experiment. METHODS: Eight exercised horses received a single intra-articular administration of 9 mg of TA. Synovial fluid samples were collected from the treated and contralateral joints prior to and up to 49 days following drug administration. Microarray and quantitative reverse transcription polymerase chain reaction analysis were used to assess changes in expression levels of various inflammatory and structural genes post drug administration. RESULTS: Drug concentrations in plasma and synovial fluid, were no longer quantifiable by 6 and 28 days following drug administration respectively. In total, the expression level of 5490 genes were significantly altered on micro array analysis, following intra-articular TA administration. Of the genes selected for further study by quantitative reverse transcription polymerase chain reaction analysis, significant changes in inflammatory genes (annexin type 1, cyclooxygenase-1 and tumour necrosis factor stimulated gene 6) and structural genes (collagen and aggrecan) were noted. CONCLUSIONS: This study supports the use of synovial fluid as a biological matrix for studying the effects of corticosteroids on gene expression. For the majority of genes studied the effects on expression relative to baseline for both inflammatory and matrix genes were prolonged relative to plasma and synovial fluid TA concentrations. Downregulation of collagen gene expression warrants the careful use of TA in horses.

Scintigraphic comparison of intra-arterial injection and distal intravenous regional limb perfusion for administration of mesenchymal stem cells to the equine foot.

REASONS FOR PERFORMING STUDY: Intra-arterial (i.a.) and intravenous (i.v.) regional limb perfusions (RLP) through the median artery and cephalic vein, respectively, have been previously investigated for administration of mesenchymal stem cells (MSCs) to the equine distal limb. Limitations due to thrombosis of the arteries after i.a. RLP and poor distribution of MSCs to the foot with i.v. RLP were observed. These techniques need to be modified for clinical use. OBJECTIVES: Evaluate the distribution, uptake and persistence of radiolabelled MSCs after i.a. injection through the median artery without a tourniquet and after i.v. RLP through the lateral palmar digital vein. STUDY DESIGN: In vivo experimental study. METHODS: (99m) Tc-HMPAO-labelled MSCs were injected through the median artery of one limb and the lateral palmar digital vein of the other limb of 6 horses under general anaesthesia. No tourniquet was used for the i.a. injection. A pneumatic tourniquet was placed on the metacarpus for i.v. injection. Scintigraphic images were obtained up to 24 h after injection. RESULTS: Intra-arterial injection resulted in MSCs retention within the limb despite the absence of a tourniquet and no thrombosis was observed. Both i.a. injection and i.v. RLP led to distribution of MSCs to the foot. The i.a. injection resulted in a more homogeneous distribution. The MSC uptake was higher with i.v. RLP at the initial timepoints, but no significant difference was present at 24 h. CONCLUSIONS: Both i.a. injection through the median artery without a tourniquet and i.v. RLP performed through the lateral palmar digital vein under general anaesthesia are safe and reliable methods for administration of MSCs to the equine foot. The i.a. technique is preferred owing to the better distribution, but is technically more challenging. The feasibility of performing these techniques on standing horses remains to be investigated.

Distribution and persistence of technetium-99 hexamethyl propylene amine oxime-labelled bone marrow-derived mesenchymal stem cells in experimentally induced tendon lesions after intratendinous injection and regional perfusion of the equine distal limb.

REASONS FOR PERFORMING STUDY: Intralesional (i.l.) injection is currently the most commonly used technique for stem cell therapy in equine tendon injury. A comparison of different techniques of injection of mesenchymal stem cells for the treatment of tendon lesions is required. OBJECTIVES: We hypothesised that vascular perfusion of the equine distal limb with mesenchymal stem cells (MSCs) would result in preferential distribution of MSCs to acute tendon injuries. STUDY DESIGN: In vivo experimental study. METHODS: Lesions were surgically induced in forelimb superficial digital flexor tendons of 8 horses. Three or 10 days after lesion induction, technetium-99 hexamethyl propylene amine oxime-labelled MSCs were injected via i.v. or intra-arterial (i.a.) regional limb perfusion (RLP) at the level of the distal antebrachium and compared to i.l. injection. Mesenchymal stem cell persistence and distribution within the forelimb and tendon lesions was assessed with scintigraphy for 24 h. RESULTS: Lesion uptake was higher with i.l. injection than with RLP, but MSC persistence decreased similarly over time in all 3 techniques. Intra-arterial RLP resulted in a better distribution of MSCs and a higher uptake at the lesion site than i.v. RLP. Limbs perfused i.a. on Day 10 showed greater accumulation of MSCs in the lesion than limbs perfused on Day 3. Arterial thrombosis occurred in 50% of the i.v. RLP limbs and in 100% of the i.a. RLP limbs, which led to clinical complications in one horse. CONCLUSIONS AND POTENTIAL RELEVANCE: Compared with i.l. injection, RLP results in lower uptake but similar persistence of MSCs at the site of tendon lesions. A time dependent accumulation of MSCs was identified with i.a. RLP. The i.a. RLP appears more advantageous than the i.v. RLP in terms of distribution and uptake. However, the described i.a. technique produced arterial thrombosis and thus cannot currently be recommended for clinical use.

Scintigraphic evaluation of intra-arterial and intravenous regional limb perfusion of allogeneic bone marrow-derived mesenchymal stem cells in the normal equine distal limb using (99m) Tc-HMPAO.

REASONS FOR PERFORMING STUDY: Mesenchymal stem cells (MSCs) are commonly injected intralesionally for treatment of soft tissue injuries in the horse. Alternative routes of administration would be beneficial for treatment of lesions that cannot be accessed directly or to limit needle-induced iatrogenic damage to the surrounding tissue. OBJECTIVES: The purpose of our study was to evaluate MSC distribution after intra-arterial (IA) and intravenous (IV) regional limb perfusions (RLP) using scintigraphy. We hypothesised that MSCs would persist in the distal limb after tourniquet removal and that both techniques would lead to diffuse MSC distribution. METHODS: Six horses were used in the study. MSCs were labelled with hexamethyl propylene amine oxime (HMPAO) and technetium-99m. RLP was performed through the median artery of one forelimb and the cephalic vein of the opposite limb under general anaesthesia. The tourniquet was left in place for 45 min. Scintigraphic images were obtained at 0, 45, 75 min, 6 h and 24 h post injection. RESULTS: Distribution of labelled MSCs through the entire distal limb was achieved with all 6 IA RLP, but 3 out of 6 IV RLP showed poor or absent uptake distal to the metacarpus. Mesenchymal stem cell persistence was 39% (30-60%) and 28% (14-50%) (median [minimum-maximum]) at 6 h for IA and IV RLP, respectively. Severe arterial thrombosis occurred in one horse after IA RLP. CONCLUSIONS: Both IA and IV RLP of the distal limb result in MSC persistence in perfused tissues. The IA perfusion resulted in more reliable cell distribution to the pastern and foot area. POTENTIAL RELEVANCE: Regional limb perfusion of MSCs might be used in cases where intralesional injection is not possible or in order to avoid iatrogenic needle damage. Further work is needed to assess the safety of IA RLP before its clinical use.

[Mild to moderate postoperative pain: the PATHOS survey results for Spain versus other European countries]. / Estudio Observacional PATHOS sobre el dolor postoperatorio leve o moderado. Comparación de los resultados de España frente a Europa.

OBJECTIVES: The Postoperative Analgesic Therapy Observational Survey (PATHOS) was designed to identify the current state of postoperative pain in specific areas and the needs and opportunities for improving treatment. We compared the results obtained in Spain with those obtained in the rest of Europe between August 2004 and June 2005. MATERIAL AND METHODS: A prospective observational multicenter, multinational study in 7 European countries. The data on postoperative pain management were obtained anonymously by means of a standardized multiple-choice questionnaire. RESULTS: Participation was higher among surgeons (68%) in Spain and among anesthesiologists (69%) in other European countries. Systematic presurgical information on the treatment of postoperative pain was provided to 22.2% of patients undergoing surgery in Spain. Organized structures for the treatment of postoperative pain are less common in Spanish hospitals (47%) than in other European hospitals (69%). Anesthesiologists are less often those who inform patients about postoperative pain in Spain than in other European countries. Only 25.9% of Spanish hospitals have written protocols for treating postoperative pain. Pain was not evaluated in 39% of patients who underwent surgery in Spain. CONCLUSIONS: There is inadequate treatment of postoperative pain, and the problem is greater in Spain than in the other European countries participating in PATHOS. The results should help to identify opportunities for improvement.

Activation of kinin B receptor triggers differentiation of cultured human keratinocytes.

BACKGROUND: Keratinocyte life span is modulated by receptors that control proliferation and differentiation, key processes during cutaneous tissue repair. The kinin B(1) receptor (B(1)R) has been reported in normal and pathological human skin, but so far there is no information about its role in keratinocyte biology. OBJECTIVES: To determine the consequence of kinin B(1)R stimulation on tyrosine phosphorylation, a key signalling mechanism involved in keratinocyte proliferation and differentiation. METHODS: Subconfluent primary cultures of human keratinocytes were used to investigate tyrosine phosphorylation, epidermal growth factor receptor (EGFR) transactivation, cell proliferation and keratinocyte differentiation. Cell proliferation was assessed by measuring bromodeoxyuridine incorporation whereas assessment of cell differentiation was based on the expression of filaggrin, cytokeratin 10 (CK10) and involucrin. RESULTS: The major proteins phosphorylated, after B(1)R stimulation, were of molecular mass 170, 125, 89 and 70 kDa. The 170- and 125-kDa proteins were identified as EGFR and p125(FAK), respectively. Phosphorylation was greatly reduced by GF109203X and by overexposure of keratinocytes to phorbol 12-myristate 13-acetate, indicating the participation of protein kinase C. B(1)R stimulation did not increase [Ca(2+)]i, but triggered EGFR transactivation, an event that involved phosphorylation of Tyr(845), Tyr(992) and Tyr(1068) of EGFR. B(1)R stimulation did not elicit keratinocyte proliferation, but triggered cell differentiation, visualized as an increase of filaggrin, CK10 and involucrin. Blockade of EGFR tyrosine kinase by AG1478, before B(1)R stimulation, produced an additional increase in filaggrin expression. CONCLUSIONS: The kinin B(1)R may contribute to keratinocyte differentiation and migration by triggering specific tyrosine signalling pathways or by interacting with the ErbB receptor family.

[Comparison of 2 techniques for inhaled anesthetic induction with sevoflurane in coronary artery revascularization]. / Estudio comparativo de dos técnicas de inducción inhalatoria con sevoflurano en cirugía de revascularización coronaria.

OBJECTIVE: Our objective was to evaluate efficacy, side effects, and hemodynamic alterations during anesthetic induction with sevoflurane in patients undergoing coronary artery bypass surgery, comparing the techniques of administration with tidal volume breathing and with vital capacity breaths. MATERIAL AND METHODS: This was a randomized controlled trial enrolling 30 patients scheduled for myocardial revascularization. Anesthetic induction with inhaled sevoflurane was performed with 2 techniques: sevoflurane administered with tidal volume breathing (n=15) and with vital capacity breaths (n=15). We assessed time until a bispectral index (BIS) of 50 or less was reached. We also recorded adverse effects and alterations in hemodynamic variables during induction. RESULTS: The time to induction was significantly shorter in the tidal volume group. The time until reaching a BIS of 50 or less was significantly shorter in the vital capacity group. Hemodynamics were similar in both groups (no significant differences). In both groups mean arterial pressure decreased significantly from baseline (P<0.05) and systolic and diastolic blood pressures both decreased slightly, with no significant heart rate or ST segment changes. Adverse effects were few and not serious. CONCLUSIONS: Mean arterial pressure decreased in both groups, with no significant differences. The results indicate that hemodynamic stability seems to be similar with both techniques for providing inhaled anesthetic induction with sevoflurane.

[Hypovolemic shock during surgery caused by a rectus sheath hematoma]. / Shock hipovolémico intraoperatorio consecuencia de un hematoma de la vaina de los rectos.

Prophylactic treatment with low molecular weight heparins (LMWH) is currently widely used to prevent thromboembolic events. However, such treatment is not free of risk. Among the possible complications described is rectus sheath hematoma. We report the case of a patient undergoing surgery for a hypophysial adenoma approached by the transsphenoidal route. He received LMWH prophylaxis for thromboembolism and showed a tendency to hypotension during surgery. The patient's condition deteriorated to hypovolemic shock accompanied by episodes of atrial fibrillation with rapid ventricular response. With the transfusion of medications, blood products and plasma volume expanders, the patient was stabilized and surgery was completed. A computed tomography scan then revealed a hematoma occupying the greater part of the left anterior rectus muscle. With conservative wait-and-see treatment the abdominal symptoms disappeared and the hematoma gradually receded until fully resolved. Spontaneous rectus sheath hematoma is a rare condition. Presentation is quite nonspecific and computed tomography is needed for reaching a firm diagnosis. When a hematoma is large, the initial clinical picture may include hypovolemic shock, which may develop during surgery if the hematoma is not diagnosed early. Intraoperative management will be much more difficult than it would have been if diagnosis and treatment had taken place before the operation.

Population dietary habits and physical activity modification with age.

OBJECTIVE: The aim of the present study was to analyse the relation between age and both dietary habits and leisure-time physical activity, and to determine nutrient inadequacy of aged groups in our population. DESIGN: Cross-sectional study. SETTING: A random sample of the 25-74-y-old population of Gerona, Spain. SUBJECTS: A total of 838 men and 910 women were selected from among the general population according to the 1991 census. OUTCOME MEASURES: Analysis of dietary habits, including amount and type of alcohol consumption, and detailed evaluation of leisure-time physical activity. RESULTS: Nutrient densities of carbohydrates, vitamin B(1), vitamin B(12), vitamin C, vitamin E, folate, potassium, iron, magnesium, copper, and dietary fiber increased significantly (P<0.05) with age in both genders, whereas an inverse trend was observed for total fat, saturated fatty acids, cholesterol, and sodium. Multiple linear regression analysis revealed a direct association of healthy dietary habits, characterized through a composite dietary score, with age after adjusting for several confounders both in men and women (P<0.001). This score was composed of folate, vitamin C, vitamin E, beta-carotene, dietary fibre, cholesterol, saturated fatty acids, and sodium. In all, 29 and 10% of male and female subjects aged 65-74 y, respectively, reported inadequate intakes of six or more of 16 nutrients. Total leisure-time physical activity increased with age in men (P<0.002), and was not different among female age groups. CONCLUSION: Dietary behaviours and levels of physical activity spent during leisure time indicate a healthy lifestyle of the aged men and women in the present population. Nutrient inadequacy observed in some aged men and women, however, deserves particular intervention of health-care programmes for this growing part of our society.

[Sedation with remifentanil for tracheostomy in a pediatric patient]. / Sedación con remifentanilo para una traqueostomía en un paciente pediátrico.

Remifentanil is an ultra-short-acting opioid that is frequently used in adults for surgical anesthesia or conscious sedation, but its use in children is much less common. We report the case of a 7-year-old boy with lateral cervical tumors displacing all cervical and facial structures. An emergency tracheostomy was performed when he developed respiratory difficulty due to partial airway obstruction. Because of the size and location of the intraoral tumors and a history of bleeding, orotracheal intubation and other airway management techniques were ruled out. The tracheostomy was performed under local anesthesia and sedation with a perfusion of 0.05 x microgKg(-1) x min(-1) provided the necessary relaxation and immobility for surgery. Sedation under observation with monitoring is among the indications of remifentanil. Spontaneous breathing is maintained with infusions less than 0.05 to 0.1 microg x Kg(-1) x min(-1). In the case we report, the patient's risk of complete airway obstruction due to bleeding upon manipulation had to be assessed and compared with the respiratory depression that might possibly have been caused by remifentanil perfusion. We judged that the option of sedation would cause less morbidity and offered greater safety for the patient. The outcome of this case is consistent with reports that remifentanil is a good option for adequately sedating children who are breathing spontaneously.

Bone formation in hydroxyapatite tricalcium phosphate ceramic implants used in the treatment of the postenucleation socket syndrome.

PURPOSE: To determine the histopathologic changes in coralline hydroxyapatite tricalcium phosphate (HA-TCP) blocks used in the treatment of the postenucleation socket syndrome (PESS). METHODS: Twenty-four patients were treated with HA-TCP blocks placed directly into the orbital fat to correct the PESS. Eight of these patients required partial removal of the material for various reasons between 32 and 371 days after the initial operation. The orbital implants were decalcified and processed for light and electron microscopic examination. RESULTS: Light microscopy demonstrated fibrovascular ingrowth into the pores of the implant in all cases. Osteogenesis was observed in three cases in the periphery of the implant. Ossification occurred in the implants after a mean implantation duration of 276 days versus 67 days in cases without ossification. CONCLUSION: Implants of HA-TCP, a new material used in ophthalmology, demonstrate the presence of fibrovascular ingrowth, reflecting the excellent biointegration of this material.

Evidence for modulation of human epidermal differentiation and remodelling by CD40.

BACKGROUND: It is widely accepted that CD40 plays a critical role in the regulation of immune response. However, the significance of CD40 expression on normal human keratinocytes is only partially known. OBJECTIVES: To perform a morphological re-examination of the role of CD40 on the differentiation of human keratinocytes and remodelling of the epidermis. METHODS: Keratinocytes were grown on fibroblasts transfected with the CD40 ligand (CD40L) to investigate the formation of epidermal sheets in culture under the influence of the CD40L. Control experiments were carried out using the same cells but transfected with CD32. Further, three specific anti-CD40 monoclonal antibodies were used as soluble agonists to analyse the effect of CD40 ligation on keratinocyte differentiation. RESULTS: Epidermal sheets developing from keratinocytes cocultured with fibroblasts transfected with CD40L but not with CD32 showed an up to 50% reduction in thickness compared with control sheets. This change depended mostly on cellular flattening and a decrease in the number of cell layers, and was coincident with a transient decrease in cell surface CD40 immunoreactivity. On the other hand, normal epidermis, and freshly isolated and cultured keratinocytes revealed a predominant CD40+/Ki-67- phenotype that was demonstrated by double immunocytochemistry. Consistent with these observations, keratinocytes primed with interferon-gamma responded to the three soluble agonists, but not to control IgG1, producing immunoreactive (pro)filaggrin and displaying morphological changes in shape and size equivalent to those seen in differentiated cells. CONCLUSIONS: As a whole, our findings provide evidence that CD40+ keratinocytes represent a poorly differentiated population, not actively engaged in the cell cycle, which under specific stimulation is committed towards terminal differentiation.

Aqueous humor and serum tumor necrosis factor-alpha in clinical uveitis.

OBJECTIVE: To study the local and systemic behavior of the tumor necrosis factor-alpha (TNF-alpha) in patients with active uveitis. METHODS: TNF-alpha levels were measured in aqueous humor and peripheral blood samples using an enzyme-linked immunosorbent assay from 23 patients with uveitis and 16 control patients who had been operated on for uncomplicated cataracts. RESULTS: Aqueous humor and sera of patients with uveitis showed higher levels of TNF-alpha than those of controls (p < 0.001). A comparison of cytokine levels between aqueous humor and sera showed significantly higher levels of TNF-alpha in serum than aqueous humor (p < 0.001). Correlation studies using the regression test for successive steps showed that serum TNF-alpha levels correlated with recurrent uveitis (r = 0.4150; p = 0.0489). CONCLUSIONS: TNF-alpha is a cytokine that participates actively in the pathogenesis of clinical uveitis. Our data emphasize the greater systemic than local participation of TNF-alpha. Finally, an elevated serum TNF-alpha seems to be associated with a recurrent pattern of uveitis.

Radial recession osteotomy for Kienböck's disease.

Sixty-eight patients underwent radial recession osteotomy for avascular necrosis of the lunate were retrospectively evaluated after an average follow-up period of 52 months. Twenty-five patients had undergone 1 or more additional procedures concurrently for treatment of Kienböck's disease. Pain diminished in 93% of patients, grip strength improved, and wrist motion was preserved; 75% of patients continued in their original occupations, including heavy labor. Surgical complications were uncommon. Four patients subsequently underwent salvage procedures, including 2 total wrist arthrodeses. Three of these 4 patients were receiving workers' compensation. One third of patients demonstrated lunate healing after joint leveling. Preliminary results suggest that concomitant lunate revascularization or vascularized bone grafting may improve the radiographic result. With rare exceptions, radial recession osteotomy relieves pain and improves function in Kienböck's disease.

Trispiral tomographic staging of Kienböck's disease.

Trispiral tomography enhances the staging of Kienböck's disease and aids in surgical planning. The clinical records, plain x-rays, and trispiral tomograms of 105 patients with Kienböck's disease were reviewed. When tomograms were used, upward revision of the classification stage was indicated in 73% of patients with stage I or stage II disease and in 10% of those with stage III disease. On tomograms, 91% of patients had lunate fractures, compared with 55% on plain films. The most common lunate fracture seen on trispiral tomograms was a transverse shear fracture that represented lunate collapse; the next most common was a midcoronal fracture that may be displaced, causing fragment extrusion palmarly or dorsally. The most common instability pattern was nondissociative proximal row flexion, seen in stage III. Indices of carpal collapse and ulnar translation may be useful in following up patients, but values vary widely among patients.

Development of a surface replacement arthroplasty for proximal interphalangeal joints.

Sixty-six surface replacement proximal interphalangeal prostheses with a CrCo proximal and an ultrahigh-molecular-weight polyethylene distal component were used in the hands of 47 patients (mean age, 58 years) over a 14-year period. There were 37 fingers with degenerative arthrosis, 16 with traumatic arthrosis, and 13 with rheumatoid arthritis. The mean follow-up period was 4.5 years (range, 1-14 years). The results based on pain relief, motion, and deformity were good in 32 fingers, fair in 19, and poor in 15. Poor results occurred primarily in fingers with previous extensive injury or static deformity. Results with a dorsal approach were better than those with a lateral or palmar approach. Component loosening at the bone-cement junction beyond a minimal radiolucent line was seen in one late x-ray. Results in individuals changed little after the first year of follow-up care, but results overall improved during the course of the study, perhaps because of improvements in surgical technique and experience.

Preiser's disease.

Nine patients with the diagnosis of unilateral Preiser's disease were seen between 1970 and 1987. The mean age of four male and five female patients was 37 years (range, 20 to 70 years). The diagnosis was based on radiographic evidence of sclerosis, fragmentation, erosion, and collapse of the proximal pole of the scaphoid. Onset was usually insidious but two had a preexisting radial hypoplasia, a third had a modest scaphoid malunion, and a fourth had a recent fall. Treatment consisted of scaphoid excision and silicone rubber prosthetic replacement in three, debridement of necrotic bone fragments in one, and different periods of cast support and observation in the remaining five. No relationship to ulnar variance was seen. Mean follow-up was 6.9 years. Of the scaphoid implants, two had subluxated, but only one was painful. In the more conservatively treated group, pain and function were only modestly limiting in four, who returned to their original occupations as did the one treated by curettage of necrotic bone in the proximal pole. One patient (case 4) was severely incapacitated because of associated severe congenital anomalies of the lower extremities. Polyaxial tomography permitted a better assessment of the degree of involvement and carpal alignment. Preiser's disease is a rare affliction of the carpal scaphoid which may involve the entire bone in avascular changes but primarily leads to fragmentation and collapse of the proximal pole. A conservative approach to treatment is favored based on this experience.

[Insulinoma. Apropos of a new case]. / El insulinoma. A propósito de un nuevo caso.

Insulinomas are rare tumors whose difficult diagnosis is usually delayed with respect to appearance of the first symptoms. The Whipple triad (symptoms of hypoglycemia, low blood glucose and rapid alleviation of symptoms after glucose administration) associated with an increase in plasma immunoreactive insulin (IRI) and low blood glucose levels constitute the diagnostic basis of insulinoma as the cause of organic hypoglycemia. Curative treatment entails surgery and its success will depend on the location of the tumor. Selective arteriography and, more recently, percutaneous transhepatic insulin determination (IRI) in the splenoportal axis have a diagnostic rate of 90%. Nevertheless, none of these topographic diagnostic methods replaces meticulous intraoperative exploration of the pancreas, which in our case was definitive for cure.

Use of human IgM derived fragments to study structures responsible for protein A-reactivity.

The protein A-binding site of human IgM was studied by affinity chromatography on SpA-Sepharose using fragments derived from a human monoclonal SpA-reactive IgM, Iz. Neither Fabmu nor (Fc) 5mu fragments were retained on the column but IgM reactivity was unaffected by thermic treatment during proteolysis. Products intermediate between IgM and (Fc) 5mu fragments produced during shorter proteolysis showed a reactivity related to their content in Fabmu regions. On the other hand mild reduction of IgM Iz to monomeric subunits results in a dramatic loss of SpA-affinity. However these subunits, like F(ab') 2mu but unlike Fab'mu fragments, showed a significant interaction with the column. Thus, the principal requirement for SpA reactivity with IgM Iz seems to be related to the presence of Fabmu regions in a polymeric state resembling native IgM.