Rapid cytotoxicity of human B lymphocytes induced by VH4-34 (VH4.21) gene-encoded monoclonal antibodies, II

We have previously described complement-independent killing of human B lymphocytes by two IgM MoAbs derived from the VH4-34 (VH4.21) gene. Analysis of 17 independently derived VH4-34-encoded MoAbs shows that B cell toxicity is not limited to the two described MoAbs, but is a general property shared by a subset of MoAbs derived from the VH4-34 gene. As observed by two independent microscopy techniques, giant membrane pores were formed on target B cells within 10–15 min of exposure to cytotoxic VH4-34-derived MoAbs. Toxicity by individual MoAb correlated directly to its B cell binding intensity measured by FACS, i.e. stronger the binding greater the killing. Sequence analysis showed that V_H region in germ-line or in near germ-line configuration was necessary but not sufficient for B cell binding. In addition, a particular sequence motif enriched in basic amino acids in the CDR3 may be required to supplement the reactivity mediated by the V_H region of the MoAb molecule. VH4-34-encoded antibodies that fulfil the above sequence requirements have cold agglutinin activity towards the i antigen of cord erythrocytes. In vivo, such anti-i/anti-B cell antibodies are rarely detected in healthy adults, but serum levels are dramatically elevated in selective pathological conditions, such as systemic lupus erythematosus and infectious mononucleosis. This strict regulation may be related to the novel and rapid mechanism of human B cell toxicity demonstrated by antibodies encoded by a single human V_H gene.     

Ninety Day Toxicity Study of Chloroacetic Acids in Rats

Ninety Day Toxicity Study of Chloroacetic Acids in Rats. BHAT, H. K, KANZ, M. F., CAMPBELL G. A., AND ANSARI. G. A. S.(1991).Fundam. Appl Toxicol. 17, 240–253. Chloroacetic acidsare produced in drinking water as a result of disinfection processes.Chloroacetic acids are also metabolites of widely usad and toxichalogenated hydrocarbons. Thus, chronic human exposure to thesechemicals is likely to occur. The objective of the present studywas to examine the toxic effects of monochloroacetic acid (MCA),dichloroacetic acid (DCA), and trichloroacetic acid (TCA) ina 90-day subchronic study in rats via oral exposure by drinkingwater. Chloroacetic acid solutions were prepared at concentrationswhich provided an approximate intake of ? the LD50 dose perday: MCA, 1.9 mM; DCA, 80.5 mM; TCA, 45.8 mM. Control rats receiveddistilled water only. After 90 days, major organs were removed,fixed, paraffin embedded, and stained. Light microscopic examinationof the major organs revealed variable degrees of alterationsin the lung and liver of all three treated groups. In the liver,morphological changes were predominantly localized to the portaltriads, which were mildly to moderately enlarged with randombile duct proliferation, extension of portal veins, fibrosis,edema, and occasional foci of inflammation. In the lungs, minimalalterations were observed as foci of perivascular inflammationon small pulmonary veins. Morphological changes in the testesand brain were seen only in the DCA treated group. Testes wereatrophic with few spermatocytes and no mature spermatozoa. Focalvacuolation and gliosis were present in the forebrain and brainstem.The results of these studies indicate that, relative to theirrespective LD50 values DCA given at 80.5 mM is more toxic thanTCA given at 45.8 mM and MCA at 1.9 mM is least toxic.     

Rapid cytotoxicity of human B lymphocytes induced by VH4-34 (VH4.21) gene-encoded monoclonal antibodies

We have previously described two human cold agglutinin MoAbs 216 and A6(H4C5), that are derived from the VH4-34 (VH4.21) gene that bind specifically to a cell surface ligand on human B lymphocytes. In this study, we report that binding of 216 and A6(H4C5) leads to rapid killing of target B cells. This complement-independent cytotoxicity was measured by three independent assays, cell viability dye uptake on FACS, ³H-thymidine uptake, and the 3(4,5)-dimethylthiazol-2,5-diphenyl tetrazolium bromide (MTT) assay. Cytotoxicity was specific for CD20⁺ mononuclear cells in human spleen and peripheral blood. The MoAbs were also cytotoxic to human B cell lines Nalm-6, OCI-LY8, Arent and SUP-B8, but not to T cell lines HuT 78 and PEER. As observed by scanning electron microscopy, membrane pores were formed within 15 min of exposure to the MoAbs. Cytotoxic activity was dependent on MoAb concentration and temperature of exposure. Killing was greater at 4°C than 37°C. Sodium azide and EDTA did not block the cytotoxic activity. No DNA fragmentation typical of apoptosis was observed. This rapid cytotoxic activity, independent of physiologic cellular processes and independent of complement, suggests a novel mechanism of cell death via membrane perturbations.     

AN ANALYSIS OF SIDE-CHAIN CONFORMATION IN PROTEINS*

The crystal structures of a number of globular proteins are currently available. An analysis of the distribution of side-chains among different allowed conformations in these proteins has been carried out. The observed conformations of individual residues are discussed on the basis of well-known stereochemical criteria. The population distribution of side-chains in different allowed regions in conformational space can be explained largely on the basis of simple steric considerations. In addition to examining the conformational behaviour of individual residues, some population distributions of conformational angles of general interest involving groups of residues have also been analyzed.     

Isolation and characterization of a gonadotropin receptor binding inhibitor from porcine follicular fluid

The presence of a gonadotropin receptor binding inhibitor in pooled porcine follicular fluid has been demonstrated. Porcine follicular fluid fractionation on DE-32 at near neutral pH, followed by a cation exchange chromatography on SPC-50 and Cibacron blue affinity chromatography, yielded a partially purified gonadotropin receptor binding inhibitor (GI-4). The partially purified GI binding inhibitor inhibited the binding of both ¹²⁵I labelled hFSH and hCG to rat ovarian receptor preparation. SDS electrophoresis of radioiodinated partially purified GI followed by autoradiography made it possible to identify the binding component as a protein of molecular weight of 80000. Subjecting ¹²⁵I labelled GI-4 to chromatography on Sephadex G-100 helped obtain a homogeneous material, Gl-5. The ¹²⁵I labelled GI-5 exhibited in its binding to ovarian membrane preparations characteristics typical of a ligand-receptor interaction such as saturability, sensitivity to reaction conditions as time, ligand and receptor concentrations and finally displaceability by unlabelled inhibitor as well as FSH and hCG in a dose dependent manner. This material could bind ovarian receptors for both FSH and LH, its binding being inhibited by added FSH or hCG in a dose dependent manner.     

The private/public mix in health care in India

Private hospitals and private medical practitioners play a significantpart in delivering health care services in India. As the demandfor health care has increased, institutions in this sector haveexpanded widely in both urban and rural areas. The relationshipbetween patient and private practitioner considerably influencesthe perceived and actual needs about health care. This relationshipis expected to play an important role in the control of diseasepatterns and management. However, the developments in this sectorhave prompted concern about the efficiency of resources, equityand access to facilities, and the availability of financingmechanisms to support private health care. Also, the efficiencywith which the resources are used in this sector has directbearing on the cost and quality of services. The existence ofthese health care institutions therefore has profound implicationsfor the present character of the Indian health care system,and its future course. The objectives of the present study are to review the role ofthe private health care sector in India and the policy concernsit engenders. The discussion suggests that policy makers inIndia should take serious note of the growing influence of theprivate sector in providing health care in India. Policy interventionsin health should not ignore their existence and this sectorshould be explicitly involved in the health management process.It is argued that regulatory and supportive policy interventionsare inevitable to promote this sector's viable and appropriatedevelopment.     

Sporadic distal renal tubular acidosis and periodic hypokalaemic paralysis in Kashmir

Abstract. Twenty-one cases of renal tubular acidosis presenting with periodic hypokalaemic muscular weakness, that were seen over an 8-year period, are presented. The biochemical features suggested a diagnosis of distal renal tubular acidosis and absence of family history with negative screening of eighteen families pointed towards the primary sporadic nature of the disorder in nineteen of the cases. Alkali and replacement potassium therapy resulted in immediate and sustained clinical recovery in all the cases.