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At least 163 records · Page 9Linked to original sources
PubMed1985

Immune complex effects on murine macrophages. II. Immune complex effects on activated macrophages cytotoxicity, membrane IL 1, and antigen presentation.

We investigated the effects of immune complexes on macrophage functions in vitro. Immune complexes inhibit lymphokine induction of both I-Ak expression and cytotoxic activity by fetal calf serum elicited macrophages during long-term (7 days) culture. In addition, induction of antigen presentation was significantly inhibited by immune complexes. Expression of membrane interleukin 1 (IL-1) (a membrane-bound bound form of the T cell mitogen required for antigen presentation by fixed cells) was minimally inhibited by immune complexes. Therefore, inhibition of antigen presentation was primarily due to effects on Ia expression rather than membrane IL 1 expression. The inhibitory effect of immune complexes was not found during short-term culture (4 to 48 hr) when activated macrophages (bearing high levels of Ia) from mice infected with Listeria monocytogenes were examined. Immune complexes maintained or even increased levels of both I-Ak and cytotoxicity in activated macrophages. The implications of these findings for immune complex modulation of the immune response are discussed.

Animals↗
PubMed1980

EPR study of heme x NO complexes of ascorbic acid-reduced Pseudomonas cytochrome oxidase and corresponding model complexes.

The EPR spectra of the NO complexes of frozen solutions of ascorbic acid-reduced cytochrome oxidase (nitrite reductase) purified from Pseudomonas aeruginosa, of its heme d1-depleted form, and of heme d1 in solutions containing various nitrogenous bases are quite similar to each other as well as to several heme (iron protoporphyrin IX)-containing proteins. The NO complexes of heme d1 (an iron-chlorin) in the presence of nitrogenous bases belong to spectral type C according to Kon's classification and, thus, the energy levels of the iron are closely related to thorse of heme complexes recorded under similar conditions. Comparison of these spectra with those of complexes of known structure suggests that both heme c and heme d1 are linked with Pseudomonas cytochrome oxidase by means of a nitrogenous ligand. The EPR spectrum of the NO complex of the native enzyme exhibits a lack of resolution of the high field (gy) resonance which can be characterized in terms of a spectral contribution from both the heme c and heme d1 moieties. The similarity between the EPR spectra of the NO complexes of horse heart cytochrome c and the heme d1-depleted Pseudomonas cytochrome oxidase before and after interaction with urea suggests structural similarities involving the heme irons. The changes caused by urea are likely to be a breaking or distortion of the bond between the iron and the protein-donated nitrogenous ligand and are similar to alterations seen with NO complexes of hemoglobin under a variety of conditions.

Ascorbic Acid↗
PubMed1981

Immune complexes in early arthritis. L Detection of immune complexes before rheumatoid arthritis is definite.

Fifty-three patients with early arthritis were studied longitudinally for up to 3 years. During this time, 24 developed sufficient features for definite rheumatoid arthritis (RA) to be diagnosed. The other (arthralgia patients) differed from the RA patients as, in the majority, C-reactive protein and ESR were normal and anti-nuclear antibodies or rheumatoid factors were rarely found. Moreover, in time their signs and symptoms improved or disappeared. Circulating immune complexes were detected in both groups of patients by the platelet aggregation test whereas complexes detected by abnormal Clq-binding activity were found mainly in the RA patients. Platelet-aggregating complexes were usually present in the first samples studied and disappeared in the arthralgia patients with recovery from their symptoms. In the RA patients, Clq-binding complexes appeared simultaneously or later than platelet-aggregating complexes but both tests were positive several months before RA could be diagnosed. These results suggest that immune complexes are one of the first immunological abnormalities to appear in patients with arthritis. Although the constituent antigen and antibody of complexes detected by either test are unknown, their possible nature is discussed.

Adolescent↗
PubMed1990

D1-D2-cytochrome b559 complex from the aquatic plant Spirodela oligorrhiza: correlation between complex integrity, spectroscopic properties, photochemical activity, and pigment composition.

A D1-D2-cyt b559 complex with about four attached chlorophylls and two pheophytins has been isolated from photosystem II of the aquatic plant Spirodela oligorrhiza and used for studying the detergent-induced changes in spectroscopic properties and photochemical activity. Spectral analyses (absorption, CD, and fluorescence) of D1-D2-cyt b559 preparations that were incubated with different concentrations of the detergent Triton X-100 indicate two forms of the D1-D2-cyt b559 complexes. One of them is photochemically active and has an absorption maximum at 676 nm, weak fluorescence at 685 nm, and a strong CD signal. The other is photochemically inactive, with an absorption maximum at 670 nm, strong fluorescence at 679 nm, and much weaker CD. The relative concentrations of the two forms determine the overall spectra of the D1-D2-cyt b559 preparation and can be deduced from the wavelength of the lowest energy absorption band: preparations having maximum absorption at 674, 672, or 670.5 nm have approximately 20, 60, or 85% inactive complexes. The active form contains two chlorophylls with maximum absorption at 679 nm and CD signals at 679 (+) and 669 nm (-). These chlorophylls make a special pair that is identified as the primary electron donor P-680. The calculated separation between the centers of these two pigments (using an extended version of the exciton theory) is about 10 A, the pigments' molecular planes are tilted by about 20 degrees, and their N1-N3 axes are rotated by 150 degrees relative to each other. The other two chlorophylls and one of the two pheophytins in the D1-D2-cyt b559 complex have their maximum absorption at 672 nm, while the maximum absorption of the photochemically active pheophytin is probably at 672-676 nm. During incubation with Triton X-100, the photochemically active complex is transformed into an inactive form with first-order kinetics. In the inactive form the maximum absorption of the 679 nm absorbing Chls is blue-shifted to 669 nm. The first-order decay of the photochemical activity suggests that the isolated D1-D2-cyt b559 complex is stable as an aggregate but becomes unstable on dissociation into individual D1-D2-cyt b559 units.

Chlorophyll↗
PubMed1995

Analysis of the pigment stoichiometry of pigment-protein complexes from barley (Hordeum vulgare). The xanthophyll cycle intermediates occur mainly in the light-harvesting complexes of photosystem I and photosystem II.

The carotenoid zeaxanthin has been implicated in a nonradiative dissipation of excess excitation energy. To determine its site of action, we have examined the location of zeaxanthin within the thylakoid membrane components. Five pigment-protein complexes were isolated with little loss of pigments: photosystem I (PSI); core complex (CC) I, the core of PSI; CC II, the core of photosystem II (PSII); light-harvesting complex (LHC) IIb, a trimer of the major light-harvesting protein of PSII; and LHC IIa, c, and d, a complex of the monomeric minor light-harvesting proteins of PSII. Zeaxanthin was found predominantly in the LHC complexes. Lesser amounts were present in the CCs possibly because these contained some extraneous LHC polypeptides. The LHC IIb trimer and the monomeric LHC II a, c, and d pigment-proteins from dark-adapted plants each contained, in addition to lutein and neoxanthin, one violaxanthin molecule but little antheraxanthin and no zeaxanthin. Following illumination, each complex had a reduced violaxanthin content, but now more antheraxanthin and zeaxanthin were present. PSI had little or no neoxanthin. The pigment content of LHC I was deduced by subtracting the pigment content of CC I from that of PSI. Our best estimate for the carotenoid content of a LHC IIb trimer from dark-adapted plants is one violaxanthin, two neoxanthins, six luteins, and 0.03 mol of antheraxanthin per mol trimer. The xanthophyll cycle occurs mainly or exclusively within the light-harvesting antennae of both photosystems.

Carotenoids↗
PubMed1987

Identification and properties of a quinol oxidase super-complex composed of a bc1 complex and cytochrome oxidase in the thermophilic bacterium PS3.

Evidence for the presence of a quinol oxidase super-complex composed of a cytochrome bc1 complex and cytochrome oxidase in the respiratory chain of a Gram-positive thermophilic bacterium PS3 is reported. On incubation with an octyl glucoside-solubilized fraction of the total membranes of PS3 anti-serum against PS3 cytochrome oxidase gave an immunoprecipitate that showed both quinol-cytochrome c reductase and cytochrome c oxidase activities. When the cholate-deoxycholate and LiCl-treated membranes of PS3 were solubilized and subjected to ion-exchange chromatography in the presence of octaethyleneglycol dodecyl ether, most of the A-, B-, and C-type cytochromes were copurified as a peak having both quinol-cytochrome c reductase and cytochrome oxidase activities. The immunoprecipitate and quinol oxidase preparation contained hemes a, b, and c in a ratio of about 2:2:3, indicating the presence of one-to-one complex of cytochrome oxidase containing 2 hemes a and one heme c, and a bc1 complex containing 2 hemes b and 2 hemes c. Gel electrophoresis in the presence of dodecyl sulfate showed that the immunoprecipitate and quinol oxidase preparation were composed of seven subunits; those of 51 (56-kDa), 38, and 22 kDa for cytochrome oxidase and those of 29, 23, 21, and 14 kDa for the bc1 complex. The 38-, 29-, and 21 kDa components possessed covalently bound heme c. The apparent molecular mass of the super complex was estimated to be as 380 kDa by gel filtration.

Antibodies↗
PubMed1986

Characterization of the monomeric and complex-associated forms of the gag-onc fusion proteins of three isolates of feline sarcoma virus: phosphorylation, kinase activity, acylation, and kinetics of complex formation.

The gag-onc fusion proteins of three isolates of feline sarcoma virus (ST-FeSV, GA-FeSV, TP1-FeSV) from a stable noncovalent complex with two cellular phosphoproteins, pp90 and pp50. These two phosphoproteins are the same phosphoproteins which have been shown to complex with the transforming proteins of Rous sarcoma virus, Fujinami sarcoma virus, Yamaguchi 73 virus (Lipsich et al., 1982), and PRCII avian sarcoma virus (Adkins et al., 1982). Both the monomeric and complex-associated gag-onc fusion proteins are phosphorylated on serine, threonine, and tyrosine; however, quantitative and/or qualitative differences in phosphorylation of the two species were apparent. Only the monomeric form of the gag-onc proteins was able to undergo tyrosine specific autophosphorylation in an in vitro kinase reaction. Both the monomeric and complex-associated forms of the proteins were acylated, the complex-associated molecules to a greater degree. Pulse-chase experiments indicated that newly synthesized gag-onc molecules become rapidly incorporated into the complex and that a significant amount of these molecules remained associated with the complex for more than 20 hr.

Acylation↗
PubMed1989

The conversion of streptokinase-plasminogen complex to SK-plasmin complex in the presence of fibrin or fibrinogen.

When equimolar amounts of Glu-plasminogen (Glu-plg) and streptokinase (SK) were mixed in the presence of S-2251, SK-plg complex was formed and only gradually converted to SK-plasmin complex. When equimolar amounts of Glu-plg and SK were mixed with fibrinogen or fibrin, Glu-plg was converted faster to plasmin suggesting that Glu-plg molecule in the complex was converted to plasmin. It is thus concluded that SK-plg complex is converted to SK-plasmin complex slowly in the absence of fibrin or fibrinogen. When SK-plg-fibrin(ogen) complex was formed, plasminogen moiety was converted to plasmin faster inside a trimolecular complex of SK, plasminogen and fibrin(ogen).

Autoradiography↗
PubMed1990

Uptake of 67copper complexed to 3H-histidine by brain hypothalamic slices: evidence that dissociation of the complex is not the only factor determining 67copper uptake.

It was previously shown that complexation of 67Cu with His facilitates 67Cu uptake by hypothalamic slices and that His, in a concentration that is 1000-fold greater than Cu(His)2, inhibits 67Cu uptake (D. E. Hartter and A. Barnea, J. Biol. Chem. 263, 799-805 (1988)). We addressed the question: Does dissociation of the Cu(His)2 complex occur during the process of Cu2+ uptake and if so, is dissociation the only factor determining uptake? Rat hypothalamic slices were incubated with 67Cu(3H-His)2 and the kinetic profiles of 67Cu and 3H-His uptake were evaluated. 67Cu uptake was linear for up to 60 min, Vo vs S [0.1-160 microM Cu(His)2] was sigmoidal, Lineweaver-Burk plot was non-linear, Scatchard plot was bell-shaped, and Hill plot had multiple slopes. In contrast, 3H-His uptake was linear for up to 30 min, Vo vs S was biphasic, Lineweaver-Burk plot was linear, Scatchard plot was biphasic, and Hill plot had a single slope. Keeping [67Cu] constant and increasing [3H-His] resulted in a dose-dependent inhibition of 67Cu uptake which was not accompanied by an inhibition of 3H-His uptake. Substituting His in the complex with Phe or Lys resulted in a marked shift to the right in Vo vs S for 67Cu uptake and at S less than 40 microM, only His facilitated 67Cu uptake relative to ionic 67Cu2+. However, Vo vs S for 3H-His, 3H-Phe, and 3H-Lys uptake were superimposeable, indicating comparable dissociation of the complexes. In summary, we demonstrate that, although complexation of Cu2+ is essential for 67Cu uptake by hypothalamic tissue, 67Cu and 3H-His are taken up by distinct processes, which implies dissociation of the complex at the level of the membrane. Moreover, even though dissociation occurs, it is not the only factor that determines Cu2+ uptake by the hypothalamic tissue. It is suggested that the physicochemical properties of the Cu complex is an important factor determining Cu uptake by brain tissue.

Animals↗
PubMed1975

Intermolecular complexes between N-methyl-1,4-dihydronicotinamide and flavines. The influence of steric and electronic factors on complex formation and the rate of flavine-dependent dihydronicotinamide dehydrogenation.

The reaction of N-methyldihydronicotinamide (NMNH) with flavine analogs saturates at high dihydronicotinamide concentrations. Complex formation between the reactants depends mainly on steric but not on electronic factors. Thus flavine analogs that differ up to 243 mV in their oxidation-reduction potential vary only between 0.09 and 0.17 M in Kd. When the flavine plane becomes blocked by bulky substituents, however, complex stability decreases by more than an order of magnitude. NMNH-flavine complexes show long wave optical absorption. The energy of the long wave transition decreases with increasing oxidation-reduction potential of the flavine as expected for charge transfer complexes. The first-order rate constants of flavine-dependent dihydronicotinamide dehydrogenation increase with increasing oxidation-reduction potential of the flavine but they are almost independent of Kd. The reaction is not subject to general acid-base catalysis. Thus flavine-dependent dihydronicotinamide dehydrogenation may be interpreted to proceed via a charge transfer complex between oxidized flavine and reduced nicotinamide. In the rate-limiting conversion of the charge transfer complex into products hydrogen is transferred directly, the rate being governed by the difference in oxidation-reduction potential between flavine and dihydronicotinamide. An alternative mechanism where the observed charge transfer complex is not on the reaction pathway appears to be improbable but cannot be eliminated.

Binding Sites↗
PubMedDate not supplied

Metal complexes of poly(alpha-amino acids). A potentiometric and circular dichroism investigation of Cu(II) complexes of poly(L-lysine), poly(L-ornithine), and poly(L-diaminobutyric acid).

The conformational properties of cupric complexes of poly(L-lysine), poly(L-ornithine), and poly(L-diaminobutyric acid) have been investigated by potentiometric, visible and UV absorption, and circular dichroism (CD) techniques. The three polymers form two kinds of complexes stable at pH less than 8.5 (type I complexes) and at pH less than 8.5 (type II complexes). It has been found that in the low pH complexes of poly(L-diaminobutyric acid) at least one deprotonated amido nitrogen is coordinated to cupric ions. Type II complexes involve always amide nitrogens in the coordination sphere of Cu(II). Evidence is presented that the structure of such complexes is not compatible with the alpha-helical conformation of the peptide backbone.

Aminobutyrates↗
PubMed1990

Superoxide dismutase and Fenton chemistry. Reaction of ferric-EDTA complex and ferric-bipyridyl complex with hydrogen peroxide without the apparent formation of iron(II).

A ferric-EDTA complex, prepared directly from FeCl3 or from an oxidized ferrous salt, reacts with H2O2 to form hydroxyl radicals (.OH), which degrade deoxyribose and benzoate with the release of thiobarbituric acid-reactive material, hydroxylate benzoate to form fluorescent dihydroxy products and react with 5,5-dimethylpyrrolidine N-oxide (DMPO) to form a DMPO-OH adduct. Degradation of deoxyribose and benzoate and the hydroxylation of benzoate are substantially inhibited by superoxide dismutase and .OH-radical scavengers such as formate, thiourea and mannitol. Inhibition by the enzyme superoxide dismutase implies that the reduction of the ferric-EDTA complex for participation in the Fenton reaction is superoxide-(O2.-)-dependent, and not H2O2-dependent as frequently implied. When ferric-bipyridyl complex at a molar ratio of 1:4 is substituted for ferric-EDTA complex (molar ratio 1:1) and the same experiments are conducted, oxidant damage is low and deoxyribose and benzoate degradation were poorly if at all inhibited by superoxide dismutase and .OH-radical scavengers. Benzoate hydroxylation, although weak, was, however, more effectively inhibited by superoxide dismutase and .OH-radical scavengers, implicating some role for .OH. The iron-bipyridyl complex had available iron-binding capacity and therefore would not allow iron to remain bound to buffer or detector molecules. Most .OH radicals produced by the iron-bipyridyl complex and H2O2 are likely to damage the bipyridyl molecules first, with few reacting in free solution with the detector molecules. Deoxyribose and benzoate degradation appeared to be mediated by an oxidant species not typical of .OH, and species such as the ferryl ion-bipyridyl complex may have contributed to the damage observed.

2,2'-Dipyridyl↗
PubMed1971

Strand-specific supercoiled DNA-protein relaxation complexes: comparison of the complexes of bacterial plasmids ColE1 and ColE2.

Certain bacterial plasmids can be isolated as unique complexes of supercoiled circular DNA and protein. These complexes are distinguished by the conversion of the supercoiled DNA to the relaxed or open-circular DNA form upon treatment with ionic detergents, proteases, or alkali. This report demonstrates that the open-circular DNA resulting from the pronase-induced relaxation of the complexes of colicinogenic factors E(1) (ColE(1)) and E(2) (ColE(2)) possesses a strand-specific break. In each case this break is found in the heavy strand of the DNA as defined by CsCl centrifugation in the presence of poly(U,G). In addition, the ColE(1) and ColE(2) complexes exhibit certain properties that are plasmid specific. Heat treatment, and to a lesser extent pronase treatment, inactivates the ColE(2) complex, making it insensitive to agents that formerly were capable of inducing relaxation (conversion of the DNA to the open-circular form). In contrast, the ColE(1) complex is not inactivated by these treatments. The potential role of these strand-specific relaxation complexes in DNA replication is discussed.

Bacterial Proteins↗
PubMed1983

Protein complexes of intermediate-sized filaments: melting of cytokeratin complexes in urea reveals different polypeptide separation characteristics.

Subunit complexes of cytokeratin polypeptides from intermediate-sized filaments (IF) of various tissues and cultured cells from rat, cow, and man were solubilized in low-salt buffer containing 4 M urea and exposed to increasing concentrations of urea, followed by urea gradient electrophoresis or two-dimensional gel electrophoresis at different urea concentrations. Correspondingly, cytokeratin polypeptides dissociated in 9.5 or 10 M urea were dialyzed into lower concentrations of urea and allowed to reassociate into specific complexes. It was found that the polypeptide constituents of a given cytokeratin complex dissociate in the form of a rather sharp "melting curve" and that dissociated polypeptides reassociate in the same mode of dependence on urea concentration. The midpoint of melting in urea (Um) is a characteristic property of a given complex of cytokeratin polypeptides. Um values differ markedly between different cytokeratin complexes, ranging from 5.9 to 9.0 M urea. The results also show that cytokeratins do not form complexes with vimentin, another type of IF protein. The data suggest that certain cytokeratin polypeptides are complementary and contain sequences that direct their association into specific complexes forming IF subunits.

Animals↗
PubMed1990

The invariant chain forms complexes with class II major histocompatibility complex molecules and antigenic peptides "in vivo".

The binding of a chicken ovalbumin peptide (residues 323-339), Ova-(323-339), to I-Ad molecules was investigated in vitro and in vivo. By using antigenic peptides labeled either with a hapten or with fluorescein, complexes formed in vitro between I-Ad and antigenic peptides were detected by Western blot analysis with an antibody recognizing the hapten 7-nitrobenzo-2-oxa-1,3-diazole and by scanning gels for fluorescence emitted by fluoresceinated peptide. Both techniques reveal that Ova-(323-339) binds not only to I-Ad alpha/beta heterodimers and separated alpha and beta chains but also to complexes of higher molecular mass. Additional analysis shows that one of these additional complexes contains I-Ad heterodimers, antigenic peptides, and also invariant chain. To explore the physiological role of these complexes, cells were incubated with haptenated peptide and the I-Ad-peptide complexes formed in vivo were purified by affinity chromatography using hapten-specific antibody. The complexes formed migrate with a significantly higher apparent molecular mass than the alpha/beta heterodimers. A band at 180 kDa contained the alpha/beta heterodimer, the antigenic peptide, and the invariant chain. These results show that in vivo high molecular mass complexes formed by the I-Ad heterodimer and the invariant chain bind antigenic peptides.

Animals↗
PubMed1993

The reference range for complexed alpha 2-macroglobulin human plasma: development of a new enzyme linked in immunosorbent assay (ELISA) for quantitation of complexed alpha 2-macroglobulin.

Purified alpha 2-macroglobulin was complexed by reaction with methylamine and used to raise monoclonal murine antibodies. A four-step enzyme linked immunosorbent assay (ELISA) was developed to determine the antibody-specificity of the produced monoclonal murine antibodies towards human native and complexed alpha 2-macroglobulin. Two monoclonal antibodies were selected, H11A11 (specific towards complexed alpha 2-macroglobulin) and 1CG4 (recognizes both forms of the molecule), and purified by affinity chromatography on protein G. The purified antibodies were used to develop a fast three-step ELISA for exact quantitation of complexed and total alpha 2-macroglobulin in human plasma. The intra-assay coefficient of variation (CV) for measurement of complexed alpha 2-macroglobulin is 2.2-9.9%, whereas the inter-assay CV was determined to be 3.7-10.5% and the recovery of the assay is 93-108%. The assay for total alpha 2-macroglobulin has an intra-assay CV of 3.0-15.5%, an interassay CV of 5.1-21.2% and a recovery of 91-116%. Citrated plasma samples from 139 healthy blood donors were examined, resulting in a reference range for complexed alpha 2-macroglobulin of 13.5-31.1 mg 1(-1) with a median value of 21.7 mg 1(-1). The concentration of total alpha 2-macroglobulin was measured by the same assay using the monoclonal antibodies 1CG4. For total alpha 2-macroglobulin we determined the reference range to be 1.12-3.54 g 1(-1) with a median value of 2.14 g 1(-1). Based on these results the reference range for complexed alpha 2-macroglobulin as a percentage of total alpha 2-macroglobulin was calculated to be 0.8-1.9% with a median value of 1.0%.

Adult↗
PubMed1990

Loss of a DNA-protein complex correlates with extinguished major histocompatibility complex class II expression in a human B cell.

An E beta DNA protein complex termed complex A, whose binding activity has recently been shown to correlate with both constitutive and regulated class II expression in murine cell lines, is also present in a human B cell, Raji. The DNA involved in complex A, which includes three previously defined transcriptional motifs, W, X, and Y, is a cis-acting transcription element in Raji cells. Both complex A binding activity and transcriptional activity of its target sequence are absent in an Ia- mutant subclone of Raji, RJ 2.2.5. This cell line, whose defect is complemented by a locus on mouse chromosome 16, reexpresses both class II and complex A upon transfection with mouse genomic DNA. We suggest that factors that form complex A or that regulate complex A formation account for the molecular lesion in this cell line.

Animals↗
PubMed1995

T cell recognition of major histocompatibility complex class II complexes with invariant chain processing intermediates.

Peptides from the lumenal portion of invariant chain (Ii) spanning residues 80-106 (class II-associated Ii peptide [CLIP]) are found in association with several mouse and human major histocompatibility complex (MHC) class II allelic variants in wild-type and presentation-deficient mutant cells. The ready detection of these complexes suggests that such an intermediate is essential to the MHC class II processing pathway. In this study, we demonstrate that T cells recognize CLIP/MHC class II complexes on the surface of normal and mutant cells in a manner indistinguishable from that of nominal antigenic peptides. Surprisingly, T cell hybrids specific for human CLIP bound to murine MHC class II molecule I-Ab and a new monoclonal antibody 30-2 with the same specificity, recognize two independent epitopes expressed on this peptide/class II complex. T cell recognition is dependent on a Gln residue (position 100) in CLIP, whereas the 30-2 antibody recognizes a Lys residue-at position 90. These two residues flank the 91-99 sequence that is conserved among human, mouse, and rat Ii, potentially representing an MHC class II-binding site. Our results suggest that the COOH-terminal portion of CLIP that includes TCR contact residue Gln 100 binds in the groove of I-Ab molecule. Moreover, both T cells and the antibody recognize I-Ab complexed with larger Ii processing intermediates such as the approximately 12-kD small leupeptin-induced protein (SLIP) fragments. Thus, SLIP fragments contain a CLIP region bound to MHC class II molecule in a conformation identical to that of a free CLIP peptide. Finally, our data suggest that SLIP/MHC class II complexes are precursors of CLIP/MHC class II complexes.

Alleles↗