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V Koistinen

Publications and source records attributed to V Koistinen.

At least 19 recordsLinked to original sources
PubMed1995

A peptide derived from the intercellular adhesion molecule-2 regulates the avidity of the leukocyte integrins CD11b/CD18 and CD11c/CD18.

beta 2 integrin (CD11a,b,c/CD18)-mediated cell adhesion is required for many leukocyte functions. Under normal circumstances, the integrins are nonadhesive, and become adhesive for their cell surface ligands, the intercellular adhesion molecules (ICAMs), or soluble ligands such as fibrinogen and iC3b, when leukocytes are activated. Recently, we defined a peptide derived from ICAM-2, which specifically binds to purified CD11a/CD18. Furthermore, this peptide strongly induces T cell aggregation mainly mediated by CD11a/CD18-ICAM-1 interaction, and natural killer cell cytotoxicity. In the present study, we show that the same ICAM-2 peptide also avidly binds to purified CD11b/CD18, but not to CD11c/CD18. This binding can be blocked by the CD11b antibody OKM10. The peptide strongly stimulates CD11b/CD18-ICAM-1-mediated cell aggregations of the monocytic cell lines THP-1 and U937. The aggregations are energy and divalent cation-dependent. The ICAM-2 peptide also induces CD11b/CD18 and CD11c/CD18-mediated binding of THP-1 cells to fibrinogen and iC3b coated on plastic. These findings indicate that in addition to induction of CD11a/CD18-mediated cell adhesion, the ICAM-2 peptide may also serve as a "trigger" for high avidity ligand binding of other beta 2 integrins.

Actin Cytoskeleton↗
PubMed1993

Effects of sulphated polyanions on functions of complement factor H.

Heparin and two dextran sulphate preparations with a low or high average molecular mass (M(r) 5000 and 5 x 10(5), respectively) enhanced binding of radioactively labelled complement factor H to the complement protein C3b, coupled to Sepharose 4B, maximally 2.5-4-fold within a polyanion concn range of 12.5-400 micrograms/ml. Despite this, heparin or low molecular mass dextran sulphate had no effect on the activity of H as a cofactor of complement factor I, when C3b bound to Sepharose 4B was used as a substrate, and high molecular mass dextran sulphate inhibited. Heparin or low molecular mass dextran sulphate had also no effect on the decay-accelerating activity of factor H on the alternative pathway C3 convertase, C3b,Bb, and high molecular mass dextran sulphate inhibited this activity, too, regardless of whether Sepharose 4B or sheep erythrocytes were used as carriers of C3b,Bb. These results suggest strongly that fluid phase heparin or dextran sulphate do not inhibit activation of the alternative pathway of complement by augmenting functions of H.

Complement C3b↗
PubMed1993

Herpes simplex virus glycoprotein C: molecular mimicry of complement regulatory proteins by a viral protein.

Herpes simplex virus (HSV) encodes a protein, glycoprotein C (gC), which binds to the third complement component, the central mediator of complement activation. In this study the structural and functional relationships of gC from HSV type 1 (HSV-1) and known human complement regulatory proteins factor H, properdin, factor B, complement receptor 1 (CR1) and 2 (CR2) were investigated. The interaction of gC with C3b was studied using purified complement components, synthetic peptides, antisera against different C3 fragments and anti-C3 monoclonal antibodies (mAb) with known inhibitory effects on C3-ligand interactions. All the mAb that inhibited gC/C3b interactions, in a differential manner, also prevented binding of C3 fragments to factors H, B, CR1 or CR2. No blocking was observed with synthetic peptides representing different C3 regions or with factor B and C3d, whereas C3b, C3c and factor H were inhibitory, as well as purified gC. There was no binding of gC to cobra venom factor (CVF), a C3c-like fragment derived from cobra gland. Purified gC bound to iC3, iC3b and C3c, but failed to bind to C3d. Glycoprotein C bound only weakly to iC3 derived from bovine and porcine plasma, thus indicating a preference of the viral protein for the appropriate host. Binding of gC was also observed to proteolytic C3 fragments, especially to the beta-chain, thus suggesting the importance of the C3 region as a binding site. Purified gC from HSV-1, but not HSV-2, inhibited the binding of factor H and properdin but not of CR1 to C3b. The binding of iC3b to CR2, a molecule involved in B-cell activation and binding of the Epstein-Barr virus, was also inhibited by the HSV-1 protein. As factor H and properdin, the binding of which was inhibited by gC, are important regulators of the alternative complement pathway, these data further support a role of gC in the evasion of HSV from a major first-line host defence mechanism, i.e. the complement system. In addition, the inhibition of the C3/CR2 interaction may suggest a possible immunoregulatory role of HSV glycoprotein C.

Antibodies, Monoclonal↗
PubMed1992

Limited tryptic cleavage of complement factor H abrogates recognition of sialic acid-containing surfaces by the alternative pathway of complement.

The potency of complement factor H (H) in accelerating the decay of the alternative pathway C3 convertase, C3b,Bb (decay-accelerating activity), was used as a measure of the affinity of native versus trypsin-treated H for the complement protein C3b bound to surfaces. When about 99% of H was cleaved at the primary tryptic cleavage site 34 kDa from the N-terminus, its decay-accelerating activity on C3b,Bb on sheep erythrocytes fell about 60-fold, whereas the trypsin-treated H was only 3-4 times less potent than native H in dissociating C3b,Bb on Sepharose 4B. The residual decay-accelerating activity, remaining after the primary cleavage, was not affected by secondary cleavage at a site 120 kDa from the N-terminus, as shown with H preparations cleaved to different degrees. Because cell surface sialic acid is known to be responsible for the high affinity of H for C3b bound on sheep erythrocytes, the results strongly suggest that the integrity of the primary tryptic cleavage site of H is essential for the recognition of sialic acid-containing surfaces by the C3b-H complex.

Animals↗
PubMed1992

Activation of the alternative pathway of complement by monoclonal lambda light chains in membranoproliferative glomerulonephritis.

Immunopathological evidence suggests that activation of the alternative pathway of complement (AP) is involved in membranoproliferative glomerulonephritis (MPGN) and in immunoglobulin A nephropathy. In this report we describe an AP dysfunction-associated factor that was isolated from the serum and urine of a patient with hypocomplementemic MPGN. Extensive glomerular deposits of C3, properdin, and of the terminal complement components were observed in the kidney of the patient. In her serum the AP hemolytic activity was virtually absent. When mixed with fresh normal serum, the patient's serum induced a 96% C3 conversion during a 30-min incubation at +37 degrees C. This activity was found to be due to a circulating factor that by immunochemical characterization proved to be a 46-kD monoclonal immunoglobulin lambda light (L) chain dimer (lambda L). Purified lambda L, but not control lambda or kappa L chains from patients with L chain disease, activated the AP in a dose- and ionic strength-dependent manner. Functionally, lambda L was differentiated from C3 nephritic factor (an autoantibody against the AP C3 convertase, C3bBb) by its inability to bind to and stabilize the C3bBb enzyme. Instead, lambda L was observed to interact directly with the AP control factor H. Thus, lambda L represents a novel type of immunoglobulin-related AP-activating factor with the capacity to initiate alternative complement pathway activation in the fluid phase.

Antibodies, Monoclonal↗
PubMed1992

Polymorphism and deficiency of human factor H-related proteins p39 and p37.

We described previously cDNA clones representing a novel factor H-related 1.4 kilobase mRNA. This mRNA species codes for a doublet of serum proteins of M(r) 39,000 and 37,000 (p39/p37). The respective recombinant proteins of the three clones H-69, pFH1.4a, and pFH1.4b differ in the expression of the epitope recognized by the monoclonal antibody (mAb) 3D11. This probably reflects the difference of three amino acid residues of the deduced protein sequence. Here we report evidence for corresponding alterations in the native proteins p39/p37 in human sera. Employing mAb 3D11 and a polyclonal factor H-specific antiserum we detected three different patterns in western blot analyses of human sera which we provisionally termed FH1.4p+m+, FH1.4p+m-, and FH1.4p-m-. In the first pattern, p39/p37 were recognized by both antibodies, while in the second pattern the two proteins reacted only with the polyclonal antiserum. Both antibodies failed to detect p39/p37 in the third pattern. These phenotypes are found in the healthy population with frequencies of 0.556, 0.40, and 0.044, respectively. The frequencies of the alleles FH1.4*p+m+, FH1.4*p+m-, and FH1.4*p-m- were estimated to be 0.33, 0.46, and 0.21, respectively, assuming the gene distribution to be in Hardy-Weinberg equilibrium. Studies of 98 members from 27 families revealed an autosomal Mendelian inheritance. Southern blot data support our assumption of a polymorphism of the factor H-related proteins p39 and p37.

Blood Proteins↗
PubMed1991

Effect of complement-protein-C3b density on the binding of complement factor H to surface-bound C3b.

Various amounts of the activation fragment C3b of the complement (C) protein C3 were coupled to Sepharose 4B by catalysis with the C3 convertase of the alternative pathway of C. The binding of radioactively labelled C proteins B and H (= factor H) to the C3b-carrying particles was assayed. It was found that the relative binding of H, but not of B, fell rapidly with decreasing densities of solid-phase C3b, suggesting a sigmoidal relationship between C3b density and binding of H. To study the phenomenon in more detail, preformed C3b was coupled to activated thiopropyl-Sepharose 6B at various densities. By using this model system, it was shown that the binding of H/unit amount of C3b was positively correlated to C3b density up to a C3b concentration of about 0.5 mg/ml of gel, whereas binding of B was independent of C3b density. The results show that accumulation of high densities of C3b on a surface creates high-affinity binding sites for H. Because H has recently been shown to form dimers in solution, the interaction of dimeric H with neighbouring C3b molecules is a likely explanation for the phenomenon. The C3b density effect may be a regulatory mechanism keeping the activation of the alternative pathway of C on activating surface within reasonable limits.

Complement C3-C5 Convertases↗
PubMed1991

Cloning of the 1.4-kb mRNA species of human complement factor H reveals a novel member of the short consensus repeat family related to the carboxy terminal of the classical 150-kDa molecule.

Three factor H mRNA species of 4.3 kb, 1.8 kb, and 1.4 kb are constitutively expressed in human liver. Having previously characterized full-length cDNA clones derived from the 4.3-kb and 1.8-kb factor mRNA, we report here the isolation and eucaryotic expression of full-length cDNA clones coding for the 1.4-kb mRNA species. The 1266-bp cDNA codes for a polypeptide of 330 amino acids and contains two polyadenylation signals and a short poly(A)+tail. The protein is composed of a leader peptide followed by five short consensus repeat domains. It shows a hybrid structure with the last three domains being almost identical to the carboxy-terminal of the classical 150-kDa factor H molecule and the two first domains representing unique short consensus repeat structures. Eucaryotic expression in COS7 cells revealed two polypeptides derived from one cDNA clone that are also found in human serum. Differences between the cDNA clones within the last three domains indicate two distinct, possibly allelic sequences that, in addition, differ from the authentic 150-kDa factor H sequence. Southern blot results support the notion that the 4.3-kb factor H and the 1.4-kb factor H-related mRNA are transcribed from two separate but highly homologous genes.

Amino Acid Sequence↗
PubMed1991

Human complement factor H: molecular cloning and cDNA expression reveals variability in the factor H-related mRNA species of 1.4 kb.

Previously, we have shown that three different mRNA species of 4.3 kb, 1.8 kb and 1.4 kb, related to human complement factor H, are constitutively expressed in the human liver. Probing with our cDNA clone H-46 which represents 920 bp of the 3' end of the 4.3 kb mRNA of factor H on human liver RNA, we always detected the 4.3 kb and the additional, abundantly expressed mRNA species of 1.4 kb in length, indicating that the 1.4 kb transcript is highly homologous to the 3' end of the classical factor H mRNA of 4.3 kb. Using H-46 as a probe, several cDNA clones were isolated from a liver cDNA library and sequenced. The open reading frame of the novel mRNA species encodes a peptide consisting of five internal short consensus repeat motifs (SCR), identifying the translational product to be a member of the SCR family. Sequence comparison with cDNA clones derived from liver RNA of a different donor provided evidence for variability in the factor H related proteins encoded by the 1.4 kb mRNA species. Interestingly, this variability was found to be restricted to the three carboxyterminal SCR domains. Expression data indicate that our variant is not recognized by the monoclonal antibody 3D11.

Amino Acid Sequence↗
PubMed1989

Truncated forms of human complement factor H.

By the use of Western-blot analyses with polyclonal anti-(Factor H) antibodies, two low-Mr protein species of Mr 41,000 and 37,000 under non-reducing conditions and 43,000 and 40,000 under reducing conditions are consistently detected together with the well-known 155,000-Mr Factor H in human plasma and serum. These two additional species are also found in plasma, urine and synovial fluids. The 41,000-Mr species but not the 37,00-Mr species is detected by a monoclonal anti-(Factor H) antibody directed at the N-terminal part of Factor H. The 37,000-Mr species but not the 41,000-Mr species is detected by a monoclonal anti-(Factor H) antibody directed at the C-terminal part of Factor H. The 41,000-Mr and 37,000-Mr species are different from the well-characterized 36,000-Mr N-terminal tryptic fragment of Factor H. They are likely to represent translational products of the short Factor H mRNA species of 1.8 kb and 1.2-1.5 kb occurring in human liver that we have recently described.

Antibodies, Monoclonal↗
PubMed1989

Common binding region of complement factors B, H and CR1 on C3b revealed by monoclonal anti-C3d.

Fab fragments of a murine C3d-specific monoclonal antibody, clone 4C2, strongly inhibited the binding of H, and up to about 80% that of B, to C3b on sheep erythrocytes, as shown by using radiolabelled purified proteins. The inhibition was also detected in the fluid phase. Conversion of C3 by preformed solid phase alternative pathway C3 convertase was not affected by 4C2. Also, it did not affect the decay rate of the convertase, but reduced the decay-accelerating effect of H on it. The results suggest that the binding sites of B and H on C3b are close to each other, and their competition for binding to C3b is focused around the C3d region. In addition, 4C2 partially blocked noncovalent binding of C3b to human erythrocytes, which suggests that CR1 also binds close to the H- and B-binding region in C3b.

Antibodies, Monoclonal↗
PubMed1983

Detection of hepatitis B surface antigen using time-resolved fluoroimmunoassay.

Conventional fluoroimmunoassay (FIA) methods based on various fluorescence principles have not achieved the sensitivity of radioimmunoassay (RIA) mainly because of problems of background fluorescence arising, for example, from the biological specimen. We now describe an immunoassay of hepatitis B surface antigen (HBsAg) based on time-resolved (TR) fluorescence using a lanthanide as label. The assay initiates the development of a new generation of immunoassays. The fluorescence intensity is measured after a selected delay time which almost completely eliminates background fluorescence, which has a fast decay time. The excitation is performed with a flashing light source. The molecules with a long fluorescent lifetime consist of chelates of rare earth metals (Eu, Tb, Sm, Dy). They absorb strongly the excitation radiation and transfer the energy to the chelated central atom which in turn produces an emission spectrum characteristic of the lanthanide used. A long Stokes' shift (greater than 270 nm) helps to reduce the background in the emission region of the chelate and thus optimizes measurement of the relevant fluorescence. The present TR-FIA uses 2-naphthoyltrifluoroacetone as chelating agent because it creates an intense fluorescence with the rare earth metals. Synergistic agents such as trioctylphosphineoxid further enhance the fluorescence of the chelate. Depending on the instrumentation used for measuring time-resolved fluorescence and the conditions used for chelate formation, lanthanides can be detected at 10(-12)-10(-14)M concentrations.

Fluorescent Antibody Technique↗
PubMed1979

Anti-HBe and subtypes of HBsAg among asymptomatic HBsAg carriers.

Finnish HBsAg positive blood donors were analyzed for the HBsAg subtype distribution and the presence of e antigen (HBeAg) and antibody to e (anti-HBe). 88% (159 of 180) of the donors had subtype and ad and 12% (21 of 180) had ay. HBeAg was found in 1% (2 of 180) and anti-HBe in 74% (133 of 180) of the donors. Anti-HBe was significantly (p less than 0.0001) more common among donors with subtype ad than with ay: 80 and 29% respectively. The mean age of donors with both subtype ad and anti-HBe was significantly (p less than 0.001) lower than that of the other donor categories.

Adult↗
PubMed1978

Use of ELISA for measuring immunoconglutinins.

An enzyme-linked immunosorbent assay (ELISA) for detection of immunoconglutinins (IKs) has been developed. IKs are allowed to bind to solid-phase C3 and are then assayed using alkaline phosphatase coupled to anti-IgG or anti-IgM. IK activity was detected in some patients' sera up to 50,000-fold dilution. Significant correlation (r = 0.65) was obtained between the levels of IgM-IKs measured by ELISA and by conventional hemagglutination assay, IgG-IKs and hemagglutination titers did not correlate (r = -0.15).

Alkaline Phosphatase↗