Semiquantitative analysis of the effects of fixation and paraffin embedding on immunoreactivity of renal basement membranes to a monoclonal antibody against type IV collagen

Alteration of collagen IV in acutely deteriorated renal allografts

BACKGROUND

The changes in the basement membrane occurring in acutely deteriorated renal allografts (ADR) have not been extensively investigated. Our purpose is to elucidate the alteration of collagen IV, a main constituent of the basement membrane in ADR.

METHODS

Fifty biopsy specimens of ADR and 10 of chronic transplant nephropathy (CTN) were examined with two monoclonal antibodies specific for collagen IV. JK199 and JK132 are monoclonal antibodies that recognize triple helical collagen IV containing the alpha1 chain. JK199 recognizes all the basement membrane containing [alpha1 (IV)]2alpha2(IV), although JK132 reacts only with a limited portion of it. In the normal kidney, JK199 reacts with the mesangial matrix, the basement membrane of Bowman's capsule (BBM), and the tubular basement membrane, as well as with the glomelular basement membrane (GBM). JK132 reacts with the mesangial matrix, BBM, and the tubular basement membrane.

RESULTS

In ADR, increased intensity of JK199 was observed in GBM, the mesangial matrix, BBM, the tubular basement membrane, and the interstitium. Increased intensity of JK132 was observed in the mesangial matrix, BBM, and the tubular basement membrane, but was not remarkable in GBM or the interstitium. In contrast, biopsy specimens of CTN showed increased intensity of JK132 in GBM, the mesangial matrix, BBM, the tubular basement membrane and the interstitium.

CONCLUSION

These results suggest that collagen IV is up-regulated in ADR. Differential staining of collagen IV with JK199 and JK132 in GBM and the interstitium may contribute to diagnose CTN.

Changes of sinusoidal basement membrane collagens in early hepatic fibrosis induced with CCl4 in cynomolgus monkeys

CCl4 was chronically administrated for 25 months to induce hepatic fibrosis in three cynomolgus monkeys so as to examine the alteration of basement membrane-related collagens during the liver injury. Although type IV collagen was immunohistochemically present along sinusoidal walls before and during the CCl4 administration, basement membrane-associated collagen (BAC), which was recognized with JK-132 monoclonal antibody, appeared around sinusoids at five to ten months of CCl4 administration. We previously developed a sandwich enzyme linked-immunosorbent assay, utilizing two monoclonal antibodies, anti-BAC antibody (JK-132) and anti-type IV collagen antibody (JK-199) [Int Hepatology Commun 1995; 4: 1-8]. The serum level of the collagen complex, which is disulfide-bridged with BAC and type IV collagen, was simultaneously monitored. The serum level of the complex at the initial stage of the examination was 19-34 ng/ml and gradually increased in relation to the intensity of immunofluorescence of BAC and type IV collagen in sinusoids and connective tissues, up to 51-57 ng/ml. The serum collagen complex levels showed a weak correlation with serum hyaluronic acid, a serum marker of hepatic fibrosis. The serum GOT, GPT, ALP and CHE levels did not reflect the alteration of sinusoids or relate to the serum collagen complex level. The increase in BAC around sinusoids and the increase of collagen complex with BAC and type IV collagen in the sera, correlate with early lesional events in hepatic fibrosis.

Optimizing collagen antigen unmasking in paraffin-embedded tissues

In order to optimize collagen antigen unmasking in paraffin-embedded tissue sections, the effects of various fixatives and duration of fixation in relation to enzyme pretreatment and microwave irradiation for collagen antigen unmasking were studied. A streptavidin-biotin-peroxidase complex method was used for the immunolocalization of type III and IV collagen antigens. Fixatives and fixation time had significant adverse effects on the immunoreactivity of the antigens. Enzyme pretreatment was found to be superior to microwave irradiation for collagen antigen unmasking. Fixation with paraformaldehyde required shorter enzyme pretreatment and yielded a more enhanced reaction than treatment with formalin and Bouin's fluid. The optimum conditions for type III and IV collagen unmasking were found to be fixation with 4% paraformaldehyde in 0.01 M phosphate-buffered saline, pH 7.4, for up to 3 weeks followed by enzyme pretreatment with 1 mg ml-1 pepsin in 0.01 N hydrochloric acid, pH 2.0, for 30 min (human tissues) or 60 min (rat tissues) at 37 degrees C. It is concluded that collagen antigen unmasking by enzyme pretreatment in tissue sections fixed for a long period of time can be successful if appropriate enzyme(s) and incubation time(s) are employed with regard to the antigen under study and fixative and fixation time used for tissue preparation.

Alveolar basement membrane breaks down in diffuse alveolar damage: an immunohistochemical study

Sequential structural changes of the alveoli in diffuse alveolar damage (DAD) were examined by immunohistochemical methods. Lung specimens obtained at autopsy from 52 patients with DAD were stained with antibodies to laminin, 7S collagen (7S) and type IV collagen (type IV) for alveolar basement membrane, to von Willebrand factor, CD-31 and thrombomodulin (TM) for the alveolar capillary endothelial cell, and to epithelial membrane antigen and surfactant apo-protein (PE-10) for the alveolar epithelium. Forty-two of the patients had the exudative form of DAD; 10 of the patients had the proliferative form of DAD. The results were summarized as follows: (i) laminin was most easily impaired both in the epithelial and capillary basement membrane in the early exudative stage; (ii) following laminin, 7S and type IV in the capillary basement membrane were also injured in the early exudative stage, and recovered in the proliferative stage; (iii) subsequently, 7S and type IV in the epithelial basement membrane were also impaired in the late exudative stage, and remained impaired even in the proliferative stage; and (iv) alveolar epithelium regenerated almost completely in the late exudative stage, but staining for TM in the alveolar capillary recovered in the proliferative stage. Because the alveolar basement membrane must govern the homeostasis of alveolar tissue architecture, it was concluded that its preservation is necessary to avoid the abnormal remodeling of the alveoli in the reparative stage of DAD, if the patient survives the acute episodes of the disease.