Specificity of IgA cold agglutinins: anti-Pr 1

Anti-Pr cold agglutinins recognize immunodominant alpha 2,3- or alpha 2,6-sialyl groups on glycophorins

Anti-Pr agglutinins (CAs) with the subspecificities anti-Pr1h, -Pr1d, -Pr2, -Pr3h, -Pr3d, -PrM and anti-Sa CAs recognize immunodominant N-acetylneuraminic acid (NeuN Ac) groups of tetra and/or trisaccharides (O-glycans) of glycophorin. These O-glycans are sialylated in alpha 2,3- and/or alpha 2,6-linkages. Sa and most Pr antigens have been inactivated by alpha 2,3-specific sialidases. Antigenicity was reconstituted on desialylated glycophorin by alpha 2,3-specific Gal beta 1,3GalN Ac-sialyltransferase indicating that alpha 2,3-linked NeuN Ac groups are the immunodominant components of Sa and most Pr antigens. Some Pr antigens were resistant to alpha 2,3-specific sialidase and were not reconstituted by alpha 2,3-specific Gal beta 1,3GalN Ac-sialyltransferase, which indicates that alpha 2,6-linked NeuN Ac group represents an immunodominant component of some Pr antigens.

Polylactosamine sugar chains expressed by epithelia of Henle's loop and collecting duct in rat and human kidney are selectively recognized by human cold agglutinins anti-I/i

Normal rat and human kidney was mapped immunohistochemically with human monoclonal cold agglutinins against the biochemically related erythrocyte glycoconjugate antigens I and i, which represent branched and linear polylactosamines, respectively. The antibodies worked well with both cryostat and paraffin-embedded material. Anti-i gave specific staining of collecting duct cells (mostly principal cells) as evidenced by double labelling with antibodies to band 3 and a 23 kD protein of intercalated cells. In contrast, anti-I turned out to be the first exclusive marker for the ascending and descending thin limb of Henle's loop. In addition, in rat kidney, the binding of anti-I/i was preserved in primary cultures both of principal cells of the papillary collecting duct and cells of the thin limb of Henle's loop. Our results suggest that both antibodies might be interesting tools for in vitro studies of renal cell physiology and the investigation of kidney development.

Anti-j: human cold agglutinins recognizing linear (i) and branched (I) type 2 chains

Two IgM lambda cold agglutinins (CAs) reacted with protease- and sialidase-resistant antigens expressed in equal strength on human adult (I), newborn (i), i adult, rabbit (I) and rhesus monkey (i) erythrocytes. The antibodies were inhibited by the linear type 2 sequence lacto-N-neotetraose and the branched type 2 sequence lacto-N-neohexaose. Endo-beta-galactosidase treatment of red cells, which splits type 2 chains from the surface, abolished CA reactivity. The CAs expressed the idiotype recognized by the anti-idiotype 9G4 specific for anti-I and anti-i CAs. The data suggest that the two CAs recognize linear (i) as well as branched (I) type 2 chains. It is proposed to term these CAs anti-j.

Anti-Sa cold agglutinin of IgA class requiring plasma-exchange therapy as early manifestation of multiple myeloma

The case of a patient (Col) with multiple myeloma presenting as chronic cold agglutinin (CA) syndrome is reported. The CA (Col) was a monoclonal IgA/k paraprotein which recognizes an antigen fully expressed in adult and newborn erythrocytes, sialidase sensitive and partially resistant to proteases. Hemagglutination-inhibition studies showed that immunodominant N-acetylneuraminic acid bound alpha 2-->3 to O-glycans of glycophorins represents the CA(Col) epitope. These serological and biochemical findings fit with the anti-Sa specificity, of which only two previous examples are known. The clinical manifestations of CA (Col) were characterized by marked acrocyanosis, generalized livedo reticularis, and incapacitating dyspnea, but only mild hemolysis. Plasma-exchange therapy was effective in quickly removing the CA and relieving the associated clinical manifestations, but such benefit was only temporary. This is the first reported example of anti-Sa CA of IgA isotype and the first case of IgA CA syndrome treated by plasma exchange.

Characterization of autoantibodies in mixed-type autoimmune hemolytic anemia

Three of 46 patients with autoimmune hemolytic anemia (AIHA) satisfied the diagnostic criteria for mixed-type AIHA in which both warm-type and cold-type autoantibodies against red blood cells (RBCs) are present. The specificities of these autoantibodies were analyzed. All of the warm-type autoantibodies were IgG-chi, and the specificities were not serologically classified. The autoantibody of patient 1 reacted to the 41- and 80-kD peptides on immunoblotting, and the epitope corresponding to it was papain sensitive. Two warm-type autoantibodies from patients 2 and 3 resembled each other in serological analyses and reacted with a protease- and neuraminidase-resistant antigen. However, the antigen corresponding to the autoantibody of patient 3 was located on the 37-kD peptide by immunoprecipitation. All of the cold-type autoantibodies were IgM-cha and showed high titer and high thermal amplitude. According to the reaction pattern with untreated and enzyme-treated RBCs, the cold-type autoantibodies of patients 2 and 3 were revealed to be anti-Om and anti-I, respectively. In patient 1, the cold-type autoantibody was characterized as having high affinity for autologous RBCs, but its specificity was unclassified. The antigens corresponding to the cold-type autoantibodies were not located by immunoblotting and immunoprecipitation. These serological and immunochemical approaches to autoantibodies in mixed-type AIHA revealed that the warm and cold components recognized the different antigens.

Neolacto (type-2 chain)-sialoautoantigens recognized by human cold agglutinins

The antigens Fl and Vo, recognized by cold agglutinins, are protease-resistant differentiation antigens like I and i antigens. In contrast to Ii, Fl and Vo are sialidase-susceptible antigens like the protease-resistant Gd antigens. Because I/i antigens are branched/linear type-2 (poly-N-acetyllactosamine or neolacto series) chains which are cleaved from red cells by endo-beta-galactosidase, the effect of the enzyme on Fl, Vo and Gd antigens was studied. Fl and Gd antigens, previously shown to be sialylated branched (Fl), and linear and branched (Gd) type-2 sequences, were not inactivated on red cells by the enzyme, whereas Vo antigenicity was completely abolished. The data suggest that Vo antigen is expressed on sialylated linear poly-N-acetyllactosamine sequence.

Cold agglutination

Autoantibodies against red cells optimally reacting at 0 degree C, ie, CA, are normally found with low titers in the serum of human adults. High-titer CA may be induced by certain infectious agents, including M pneumoniae, EBV, CMV, and rubella virus, or may develop on the basis of chronic (malignant) B cell lymphoproliferation. The main clinical manifestation of cold agglutination is AIHA. Antigens and antibodies of cold agglutination are the best characterized reaction partners of a human autoimmune process. CA may recognize I and i antigens, which are lipid- and protein-linked branched and linear N-acetyl-lactosamine chains, respectively. They are precursors of the ABH blood group antigens and are converted into H by fucosylation. An alternative substitution by sialylation creates Gd, Fl, and probably Vo/Li antigens. CA with anti-Pr and anti-Sa specificities recognize 0-glycans with immunodominant sialyl groups on glycophorins. Several Pr subspecificities can be identified by chemically modified sialyl groups on glycophorins. Because CA in chronic lymphoproliferation are monoclonal antibodies, structure-specificity-interrelations of the antibodies could be identified by primary structure analyses of the N-terminal variable regions of H and L chains and by studies on CA idiotypes. Interrelations between distinct CA specificities and particular infectious agents could explain cold agglutination as a response to receptors for the agents or to the binding sites of antibodies against the agents. Interrelations also existing between certain CA isotypes (Ig classes and L chain types) and CA specificities could be a basis for the elucidation of the enigmatic etiology of chronic (malignant) monoclonal cold agglutination.

A human monoclonal IgM kappa cold agglutinin recognizing oligosaccharides with immunodominant sialyl groups preferentially at the blood group M-specific peptide backbone of glycophorins: anti-PrM

A kappa-monotypic IgM high titer cold agglutinin reacting like anti-Pr at low, like anti-M at higher temperatures, is described. It recognizes tetra- and/or trisaccharides with immunodominant sialyl groups on glycophorins A, B, C like anti-Pr. Its affinity to the oligosaccharides is, however, approximately 10-fold increased when they are attached to the M-specific peptide backbone of glycophorin A. The antibody, termed anti-PrM, occurred in a blood group MN patient with chronic cold agglutinin disease and caused autoimmune hemolytic anemia.

Two examples of low ionic strength-dependent autoagglutinins with anti-Pr1 specificity

Two low ionic strength-dependent autoagglutinins were studied and found to have anti-Pr1 specificity. This specificity was determined by studies with enzyme-treated and neuraminidase-treated human red blood cells (RBCs), animal RBCs and chemically-modified sialoglycoproteins, all suspended in a low ionic strength solution (LISS). Both IgM complement-binding cold agglutinins had a wide thermal range and caused in vitro hemolysis of some LISS-suspended RBCs at 37 degrees C. Compatible blood was found for these patients by using techniques that did not employ LISS.

Autoimmune hemolytic anemia by coexisting anti-I and anti-Fl cold agglutinins

In association with atypical pneumonia, a patient developed acute severe autoimmune hemolytic anemia. Hemoglobin temporarily was only 7.0 g/100 ml, so that the patient needed red blood cell (RBC) transfusion. Hemolysis was found to be caused by high titer cold agglutinins (CA), which occurred transiently during the acute period of the disease. CA of two different specificities, anti-I and anti-Fl, were demonstrated in the patient's serum. Antibodies of the two specificities were clearly separated by absorption/elution experiments using neuraminidase (RDE)-treated RBC. They were distinguished by serologic means: Both anti-I and anti-Fl react more strongly with adult RBC than with newborn and i adult RBC; in contrast to anti-I, anti-Fl does not agglutinate RDE-treated cells. Inhibition experiments showed that I-active substances prepared from papainized RBC exhibited both I and Fl antigenic activity. By RDE-treatment of I-active substances, Fl-activity was markedly reduced, while I-activity was increased.

The reactivities of human erythrocyte autoantibodies anti-Pr2, anti-Gd, Fl and Sa with gangliosides in a chromatogram binding assay

The thin layer chromatogram binding assay was used to study the reaction of several natural-monoclonal autoantibodies which recognize sialic acid-dependent antigens of human erythrocytes. Immunostaining of gangliosides derived from human and bovine erythrocytes was achieved with four autoantibodies designated anti-Pr2, anti-Gd, Sa and Fl, each of which has a different haemagglutination pattern with untreated and proteinase-treated erythrocytes and with cells of I and i antigen types. From the chromatogram binding patterns of anti-Pr2 with gangliosides of the neolacto and the ganglio series, it is deduced that this antibody reacts best with N-acetylneuraminic acid when it is alpha 2-3- or alpha 2-6-linked to a terminal Gal(beta 1-4)Glc/GlcNAc GlcNAc sequence and to a lesser extent when it is alpha 2-3-linked to a terminal Gal(beta 1-3)GalNAc sequence or to an internal galactose and when it is alpha 2-8-linked to another, internal N-acetylneuraminic acid residue. The other three antibodies differ from anti-Pr2 in their lack of reaction with glycolipids of the ganglio series. They react with the NeuAc(alpha 2-3)Gal(beta 1-4)Glc/GlcNAc sequence as found in GM3 and in glycolipids of the neolacto series, but show a preference for the latter, longer sequences. Thus all four antibodies react with sialylated oligosaccharides containing i type (linear) and I type (branched) neolacto backbones. Fl antibody differs from the other three in its stronger reaction with branched neolacto sequences in accordance with its stronger agglutination of erythrocytes of I rather than i type. The four antibodies show a specificity for N-acetyl- rather than N-glycolyl-neuraminic acid.

Characterization of an epitope (determinant) structure in a developmentally regulated glycolipid antigen defined by a cold agglutinin Fl, recognition of alpha-sialosyl and alpha-L-fucosyl groups in a branched structure

The antibody Fl shows preferential reactivity with adult erythrocytes over newborn erythrocytes, and its reactivity is abolished by sialidase treatment of the erythrocyte. The antibody was found to recognize binary determinants linked to the branched lacto-N-isooctaosylceramide (formula; see text) The presence of an N-acetylneuraminyl group at one end and L-fucosyl group at the other end is essential for the reactivity of the antibody. A substitution at the penultimate D-galactosyl residue of one of the chains with an alpha-D-(1 leads to 3)-linked 2-acetamido-2-deoxygalactosyl or galactosyl group did not inhibit the reactivity of the antibody. The new blood group A- and B-active, branched gangliosides are also isolated and characterized.

A new method for the preparation of anti-idiotypic antibodies against six different human cold agglutinins

A method based on sequential immunoadsorption for the preparation of a highly specific antibody directed against the idiotypic determinant of human cold agglutinins (CA) is described. In the present study, human cold agglutinins (CA) were used as a model, but the method can easily be adapted for the preparation of anti-idiotypic antibodies against other monoclonal human immunoglobulins. Since regenerable immunoadsorbents were used, the isolation can be accomplished even with rather low amounts of the respective immunoglobulin.

Monoclonal anti-idiotype antibodies against lymphoma-associated cold agglutinins

Hybridomas secreting monoclonal antibodies against purified cold agglutinins (CA) from lymphoma patients were screened by a cold hemagglutination inhibition test. Supernatants from positive clones were further tested against several purified CA and paraproteins of different immunoglobulin (Ig) classes. It was shown that most monoclonal antibodies raised by immunization with CA had reactivity against the constant region of IgM. However, clone H-1 produced an anti-idiotypic antibody that reacted exclusively with the CA used for immunization. Using this anti-idiotype antibody, the idiotype could be demonstrated on 25% of the patient's peripheral mononuclear cells. So far, the idiotype could not be demonstrated on the patient's T-cells. Monoclonal antibodies against lymphoma idiotypes are powerful tools for studying the immunobiology of these malignancies and may be useful as specific therapeutic reagents.

Identification of a cold agglutinin with anti-Pr3 specificity

An apparent monoclonal IgM, kappa-cold agglutinin with anti-Pr specificity was detected in the serum of a 38-year old woman. Haemagglutination inhibition studies disclosed the subspecificity anti-Pr3, since the cold agglutinin was strongly inhibited by carbodiimide-treated erythrocyte glycoproteins. Studies with animal cells showed that the corresponding Pr3 determinant was found only on human red cells. This is in contrast to earlier findings and indicates that distinct fine specificities within anti-Pr3 antibodies might well exist.

Autoimmune haemolytic anaemia with monoclonal IgM (kappa) anti-P cold autohaemolysins

A patient is described with immunoblastic non-Hodgkin's lymphoma and autoimmune haemolytic anaemia of the cold autoantibody type. The autoantibodies were monoclonal IgM-kappa cold haemagglutinins/haemolysins with blood-group specificity, anti-P. Red-cell autoantibodies directed against blood-group-P antigen have until now only been detected, as polyclonal IgG antibodies, in paroxysmal nocturnal haemoglobinuria.

A further cold agglutinin, F1, recognizing a N-acetylneuraminic acid-determined antigen

A cold agglutinin, F1, reacted with an erythrocyte antigen, which was inactivated by neuraminidase. It resembled anti-I antibodies in reacting more strongly with erythrocytes of adults than with cord blood cells. However, unlike I, this 'new' antigen is destroyed by neuraminidase treatment. This antigen is also distinct from Pr, Gd and Sa type antigens which are equally expressed on cord and adult erythrocytes.

Failure of IgA cold agglutinin to activate C

No complement (C) activation was observed when IgA cold agglutinin was reacted with its antigen on RBC. Neither C-consumption (CH50) nor C1 binding (classical pathway) nor conversion of factor B or C3 (alternative pathway) could be detected. In contrast, IgM cold agglutinins under the same conditions did activate the classical pathway. If the IgA was heat aggregated it was able to activate the alternative pathway as evidenced by factor B and C3 conversion. The result is consistent with the absence of in vivo hemolysis in patients with IgA cold agglutinins.

Inhibition of human anti-Gd cold agglutinins by sialyllactose

Two examples of IgM kappa-monotopic cold agglutinins occurring in patients with non-Hodgkin lymphomas, reacted with erythrocyte autoantigens, which were protease-resistant but were inactivated by neuraminidase. The cold agglutinins were inhibited by the trisaccharide sialyllactose [NeuNAc(alpha,2 leads to 3) Gal (beta, 1 leads to 4)Glc], which is not related to oligosaccharides known to inhibit anti-I/-i cold agglutinins, Anti-Pr cold agglutinins are not inhibited by sialyllactose, although N-acetylneuraminic acid (NeuNAc) is an essential component not only of Gd but also of Pr determinants. Gd determinants are not bound to erythrocyte membrane glycoproteins, but are apparently bound to membrane glycolipids (gangliosides).

Variable-region subgroup and specificity of cold agglutinins

The variable-region subgroup determined by amino acid sequence analysis of heavy and light chains of two monoclonal cold agglutinins with the new anti-Gd specificity is reported. Both proteins belong to the VHIII subgroup of heavy chains; one light chain falls into the V kappaI subgroup, the other has a blocked N-terminus which so far has not been observed in human kappa chains. The comparison of anti-Gd with anti-I/-i or anti-Pr cold agglutinins indicates that anti-Gd differs from other cold agglutinins with respect to variable-region subgroup. The data extend previous findings on the restriction of certain antibodies to distinct variable-region subgroups.

Serological identification of the new cold agglutinin specificity anti-Gd

The specificity anti-Gd of human cold autoagglutinins is characterized using untreated and enzyme-treated human red blood cells. Gd determinants of human RBC are resistant to proteases, but are inactivated by neuraminidase (RDE). In contrast, I/i determinants are not inactivated by proteases or RDE, while Pr1-3 determinants are inactivated by proteases and RDE, and Pra determinants are resistant to RDE, but are inactivated by proteases.

Actual aspects of cold agglutination

Cold agglutinins (CA) can be directed against antigens of the I/i system and the Pr complex. In addition, anti-Gd CA have been recently described. The CA immunoglobulins, serological specificities and the antigen immunochemistry are reviewed. CA permitted studies on interrelations between antibody structures and specificities. The significance of subgroup preferences and cross-idiotypic specificities is discussed. Interrelations between CA specificities and certain virus infections are pointed out, and recent results obtained from studies using CA as indicators for membrane alterations of other than red cells are reviewed.

A new case of monoclonal IgA kappa cold agglutinin with anti-Pr1d specificity in a patient with persistent HB antigen cirrhosis

A new case of cold agglutinin disease in a patient who had a long lasting Raynaud's phenomenon without hemolysis and a persistent HB antigen cirrhosis, is reported. The cold agglutinin is a monoclonal IgA kappa antibody which reacts at 4degreesC to a titer of 256. As the three other cases described in the literature, it demonstrates Pr1 specificity. The eluate from human cells reacts with rat and dog cells whose receptor is destroyed by both papain and neuraminidase, thus eliciting the characteristic Pr1d specificity.

Anti-Pr3: serological and immunochemical identification of a new anti-Pr subspecificity

A monoclonal IgM(kappa) anti-Pr cold agglutinin occurring after a rubella infection is shown to have the 'new' anti-Pr subspecificity anti-Pr3. Pr3 determinants are found on cat and sheep erythrocytes which lack Pr1 and Pr2 determinants. By carbodiimide treatment of human erythrocyte glycoproteins, which causes intramolecular coupling of N-acetylneuraminic acid carboxyl groups and nucleophilic centers of the glycoprotein backbone, Pr3 antigen activity is strongly increased, while Pr1 and Pr2 determinants are inactivated.

The I antigen of human red cell membrane

A high-active I antigen was isolated from human red cells after papainization. Investigations on its chemical composition and its serological properties are reported. 1. The I antigen activity was clearly demonstrated by hemagglutination inhibition studies and by the immuno-double-diffusion with all available anti-I sera. 2. The I antigen did not react with other antibodies directed against red cell antigens thus proving its specificity. Any relationships to antigen activities within the Pr-1/Pr-2, MN, and ABO systems could be excluded. 3. The substance was shown to be a glycoprotein and not a glycolipid. This was confirmed by different delipidation procedures promoting always an increase of I activity. The delipidized material contained only traces of fatty acids, and did not move on thin-layer chromatography in solvent systems normally used for glycolipid development. 4. The I determinant resides on alkali-stable oligosaccharide chains. The main sugars are galactose and N-acetylglucosamine which might be involved in the immunodeterminants.