Cause Of Incompatibility Research Articles

EVALUATION OF INCOMPATIBLE CROSSMATCHES AT A TERTIARY CARE HOSPITAL IN CHENNAI – A PROSPECTIVE STUDY

Objectives: The primary goal in blood transfusion is that the transfused blood unit be compatible with the patient during crossmatching. This compatibility testing is performed before every administration of blood component. This cross-matching test helps to detect the presence of antibodies in the recipient against antigens over red blood cells of donor. The aim of this study was to evaluate the incidence and causes of in compatible crossmatches in patients by tube agglutination method. Methods: This was a retrospective cross-sectional study conducted by analyzing incompatible crossmatches encountered during routine compatibility testing between January and December 2021 at the Department of Transfusion Medicine, Government Kilpauk Medical College and Hospital, Chennai, Tamil Nadu, India. The analysis was done in March and April 2022. All crossmatches were done by tube agglutination technique. Data were entered in Microsoft Excel and analyzed. Descriptive statistics were given in summary statistics. Results: Out of the total of 12943 crossmatches performed, 0.3% (n=39/12943) were incompatible. About 76.9% (n=30/39) were seen in females while 69.2% (n=27/39) were seen in the age group 20–60 years. About 35.9% (n=14/39) of the incompatible crossmatches were due to autoimmune hemolytic anemia (AIHA). A root cause analysis protocol was formulated to resolve the incompatibility and ensure safe transfusion. Conclusion: AIHA was the most common cause of incompatible crossmatch. The root cause analysis protocol involves a thorough evaluation of the patient’s clinical condition, underlying pathology, and errors during technical procedure to identify the cause of incompatibility. Protocols should be developed in each blood center and a logical stepwise approach will enable the provision of safe transfusion.

A case of haemolytic disease of the fetus and newborn attributed to a novel antigen in the RHAG blood group system

AbstractBackground and ObjectivesA newborn presented with jaundice in Thailand. The cord red cells tested positive by direct antiglobulin test (DAT) for an unknown maternal red cell antibody. Initial blood group sequencing suggested that the infant carried a novel variant RHAG c.140T>C, responsible for a low‐prevalence antigen in the RHAG blood group system (ISBT 030). We report here on testing of samples from the infant's parents and older sibling to define a new antigen in the RHAG system.Materials and MethodsMassive parallel sequencing (MPS) using a custom‐designed panel was performed on all four family members. Extended serological testing was also performed to determine whether family members with the same variant as the infant showed reactivity with the antibody in the maternal plasma.ResultsWe identified a novel single nucleotide variant (SNV) (RHAG c.140T>C, p.[Phe47Ser]) in samples from three of the four family members tested (the infant, the older sibling and the father). The variant was not detected in the mother's sample. Maternal plasma showed positive agglutination with all family members tested; however, when tested with routine panel cells, no reactivity was observed.ConclusionThis case study showed that the presence of the novel variant (RHAG c.140T>C), encoding a p.(Phe47Ser) change in the RhAG glycoprotein, was the apparent cause of incompatibility between maternal plasma and that of red cells from the proband, father and older sibling of the proband. We propose this variant to be a new low‐prevalence antigen in the RHAG blood group system.

A New Model Supporting Stability Quality of Materials and Industrial Products.

Stabilizing the quality of industrial product materials remains a challenge. This applies mainly to new or significantly modified materials. It also refers to special processes. The tests of product quality can stabilize the quality of industrial product materials. The popular method for this is using the non-destructive testing (NDT). The NDT identifies incompatibility but does not determine the cause of its occurrence. Hence, it was necessary to support the process of identifying causes of incompatibilities in products. The purpose of the article was to develop a model based on a new approach to determine the ranking of actions that are possible as part of the process of stabilizing the quality of industrial products. The model was developed to improve quality through sequential and systematic methods of identification (and reduce) and incompatibility. The quality management techniques and decision method were applied and combined in this model, i.e., SMART(-ER) the method, method of selecting a team of experts, brainstorming (BM), Ishikawa diagram with the 5M rule, Likert scale validation technique, arithmetic average, and Grey Relational Analysis (GRA). The test of this model was carried out to find cracks in the outer hull of 418 alloy four-point bearing (CPW-S 5616), which was identified by NDT (magnetic-powder method). As a result, a ranking of activities was obtained to stabilize the quality of the product and the main cause of incompatibility was indicated, i.e., the cause which can influence to the most degree influence on occurrence the incompatibility. The originality of the proposed model is an application in the right order of specially selected and combined qualitative methods and supporting decision methods. The finding of causes of incompatibility of products is the basis of product improvement in the area of stabilizing the quality of materials, mainly by the occurrence of special processes. The universality of the model refers to the possibility of its application for any material, processes of its formation, and processes of products, and any incompatibilities where the model can be integrated with quality control.

An approach to incompatible cross-matched red cells: Our experience in a major regional blood transfusion center at Kolkata, Eastern India.

INTRODUCTION:With the increased utilization of immunohematology (IH) analyzers in the transfusion medicine, type, and screen policy is the method of choice. Still, the importance of routine crossmatching could not be overruled. Here, we tried to understand the clinical conditions and safety of red cell transfusion and their outcomes.MATERIALS AND METHODS:This prospective study was conducted by IH laboratory, Medical College Kolkata, Blood Bank from October 1, 2015 to March 31, 2016. A set of 3cc ethylenediaminetetraacetic acid and clotted blood samples of the patients were received according to sample acceptance criteria. Blood grouping by conventional tube technique followed by crossmatching was performed by column agglutination technology (CAT) in polyspecific (IgG + C3d) gel media. Any positive result was rechecked in duplicate with additional two group-specific donor units. The persistent incompatibility was further evaluated using direct anti-human globulin test, auto control, antibody screening, and antibody identification by CAT.RESULTS:On the evaluation of 14,387 sets of patients' sample, only 100 were found to be incompatible (0.69%). Incompatibility rate is higher in females (59%). Eighty-five of these patients were repeatedly transfused. Only 38% of incompatible crossmatch were positive on indirect anti-human globulin test/antibody screening. Antibody could be identified in 16 of them. Seventeen of 100 incompatible samples (17%) presented with panagglutination, were managed with Rh, Kell phenotype/best-matched red cell units. In these 16 patients, 23 alloantibodies were identified; allo anti-E was the most common.CONCLUSION:This study showed antibody against the Rh system as the most common cause of incompatibility.

Comparison of genotyping by sequencing and microsatellite markers for unravelling population structure in the clonal fungus Verticillium dahliae

Microsatellite genotyping of a large sample of isolates of Verticillium dahliae from diverse locations recently identified seven distinct genotypic clusters. However, these clusters were not put in the context of phenotypes known to be correlated with clonal lineages in V. dahliae. The objective of this study was to compare clusters defined by microsatellite markers with clonal lineages defined by single‐nucleotide polymorphisms (SNPs) and vegetative compatibility groups (VCGs). Genotyping isolates known to belong to specific clonal lineages (based on SNPs) with microsatellite markers determined the correspondence of clusters and lineages. All but one cluster corresponded to a known clonal lineage, allowing analysis of correlations of phenotypes with microsatellite genotypes from other studies. As shown previously, most race 1 isolates are in lineage 2A, and most isolates with the defoliating pathotype are in lineage 1A. Phylogenetic incompatibility was used to test for recombination or homoplasy caused by hypervariable microsatellite loci; incompatibility was highly correlated with the number of alleles per locus, suggesting that homoplasy caused by parallel evolution of microsatellite alleles is the cause of incompatibility. Microsatellite genotyping of lineage 1A isolates from cotton and olive in Spain over a 29‐year period revealed remarkably little variation; these markers did not mutate enough to provide insight on the spatial and temporal expansion of this clone. Overall, this study showed that microsatellite genotyping can be used to identify clonal lineages in V. dahliae, which has predictive power for inferring phenotypes of phytopathological relevance such as race and pathotype.

INKOMPATIBILITAS ASAS PENGATURAN SISTEM PEMILU DENGAN SISTEM PEMERINTAHAN PRESIDENSIAL DI INDONESIA

This study examines, first, whether the principles contained in the Electoral Act Norms are incompatible with the presidential system of government? Second, what is the cause of the incompatibility between the electoral system and the presidential system? Third, what are its influences in the practice of the implementation of presidential system of government which is based on the 1945 post-amendment? This study uses normative legal research (doctrinal) focusing on literature data. The study concluded that, first, the principles of the electoral system and the presidential system of government did not support each other as one integrated system. Second, the cause of incompatibility between these two systems was because the norms and provisions in the legislation governing the electoral systems of its principles were incompatible with the principles of presidential system of government. Third, the effect was not able to support the effectiveness of the course of the practice of the organization of presidential system of government which is based on the 1945 post-amendment.

The AQP1 mutation c.601delG causes the Co-negative phenotype in four patients belonging to the Romani (Gypsy) ethnic group.

The Colton blood group antigens Co(a), Co(b) and Co3 are encoded by the AQP1 gene which produces a water channel forming integral protein. The extremely rare Co-deficiency enables immunisation against the Co3 isoantigen. Four patients from different regions of Europe who belong to the ethnic minority of Romani (Gypsy) presented with irregular antibodies against a high frequency red blood cell antigen. Positive cross-matches with all red blood cells tested were reported. An Anti-Co3 antibody was identified as the cause of incompatibility in the four cases. The genetic background was determined by polymerase chain reaction typing with sequence-specific primers and by DNA sequencing. The Co(a-b-) phenotype was confirmed in the four patients despite the fact that genotyping revealed the CO*01 allele of the AQP1 gene. A homozygous AQP1 c.601delG mutation, leading to a frame shift and producing a premature stop in the next codon, was responsible for the Co-negative phenotype in all four cases. While one patient was successfully transfused with blood from his sibling with the identical mutation, another case, a baby affected by haemolytic disease of the newborn, recovered without transfusion. Despite the difficulties in undertaking a population study to determine the prevalence of this AQP1 c.601delG allele in the ethnic minority of Romani, the observations described in this report clearly suggest an accumulation of this mutation, which causes the Co(a-b-) phenotype, in Romani (Gypsy) patients. Further studies are necessary to prove such an accumulation.

Preliminary results of the application of gonadal tissue transfer in various chicken breeds in the poultry gene conservation

The aim of the study was to devise a technique to allow transfer of ovarian and testicular tissues obtained from one day old chicks to recipient animals. The following combinations of chicken breeds were used: Tetra SL/Tetra SL, Tetra SL/Harco, Tetra SL/Black Transylvanian Naked Neck, Godollo New Hampshire/Speckled Transylvanian Naked Neck (recipient/donor), respectively. Only animals less than 24h old from hatching were used as either recipient or donor. Eggs yielding recipients were treated with busulfan to hinder the development of the recipient's own gonads. Gonads were transferred surgically to the new host which was then immunosuppressed for two months. The animals were checked at 8 or 16 weeks for the existence of implanted gonads, and if found, the gonads were removed for histology examination.Tetra SL/Tetra SL pairing resulted in successfully adhered and functioning gonads in most cases. In other combinations, no gonads originating from the donors were found in the recipients. We conclude that not all breeds seem to be suitable recipients; some breeds or individuals may show incompatibility to each other and further examination is needed to find the cause of incompatibility and to establish a suitable breed combination, which can be used for gonad transfer.

El difícil encaje de la causa de incompatibilidad sobrevenida en la institución del mandato representativo

A lo largo de los diez años de vigencia de la Ley Orgánica de Partidos Políticos han sido muchos los intentos del entorno político de ETA de salvar los efectos de la Ley y hacerse presente en las instituciones democráticas. En más de una ocasión han tenido éxito. Una vez celebrados los comicios, el daño ya estaba hecho pues la posterior constatación de connivencia con los terroristas no impedía que los electos continuaran en el ejercicio de su cargo y por lo tanto ETA estuviera presente en las instituciones democráticas. La reforma de la LOREG con la introducción de una causa de incompatibilidad sobrevenida viene a cerrar esta posibilidad. Este trabajo analiza la adecuación al CEDH de esta medida.During the ten year life of the Political Parties Law, there have been many attempts of ETA’s political environment to circumvent the Law and make itself present in democratic institutions. On more than one occasion, they have been successful. If after the election it was proved the connection between ETA and the party with which the elected participated in the electoral process, it was not possible to remove the elected from its office. After election the harm was done, and ETA could remain in public institutions. LOREG’s reform in 2011 has closed this possibility establishing the «so called» supervening cause of incompatibility. This paper analyzes the compatibility of this measure with the ECHR.

Ｌ-システインが引き起こす注射用メロペネムとアミノ酸輸液製剤の配合変化

After meropenem hydrate (MEPM) injection and amino acid infusions are mixed, the MEPM residual ratio sequentially decreases. This incompatibility is probably due to the nucleophilic attack on the β-lactam ring of MEPM by L-cysteine (L-Cys) present in the amino acid infusion. This study aims to identify the influence of L-Cys on the reaction between MEPM injection and amino acid infusions through an initial incompatibility test between MEPM and L-Cys at pH 4 to 8, followed by an incompatibility test between MEPM injection (MEPM plus additives) and 18 types of amino acid infusions. In the MEPM and L-Cys incompatibility test, as the pH increased, the MEPM decomposition speed was observed to increase after mixing of the two components. This reaction progressed as a secondary reaction, the linear relationship between pH and the logarithm of secondary reaction speed constant, k2, was established (ln k2 = 1.632 × pH － 15.631, r2 = 0.998). In the incompatibility test between MEPM injection and amino acid infusions, as the concentration of L-Cys increased, the MEPM residual ratio was observed to decrease. At 10 and 30 minutes after the mixture of components, a strong correlation was observed between the estimated MEPM residual ratio from the reaction velocity and the measured value (10 minutes: r2 = 0.985, RMSE: 5.44％; 30 minutes: r2 = 0.986，RMSE: 4.55％). The results above indicate that the residual ratio of MEPM obtained through the L-Cys incompatibility test matches the measured residual ratio of MEPM using the MEPM injection and amino acid infusions. Therefore, L-Cys has been identified as the main cause of incompatibility between MEPM injection and amino acid infusions.

Differential and integrated form consistency in 1-D phenomenological models for shape memory alloy constitutive behavior

Shape memory alloys are being explored increasingly for developing smart structures and devices in aerospace, automotive and other application areas. The material behavior is highly nonlinear with coupled thermomechanical response involving temperature and/or stress induced phase transformations. Modeling the constitutive behavior of these materials poses several challenges and a few phenomenological models exist that provide a quick and reasonable approach to assess their behavior. Due to phenomenological approach, several assumptions are made in order to simplify the model and some of them introduce inconsistencies or anomalies into the model. In this paper, a frequently used approach, namely, Brinson [Brinson, L.C., 1993. One dimensional constitutive behavior of shape memory alloys: thermomechanical derivation with non-constant material functions and redefined martensite internal variable. J. Intell. Mater. Syst. Struct. 4(2), 229–242.] model, is investigated. The constitutive equation is usually expressed at the outset in the differential form and the integrated form of the same is obtained. It is shown that the two forms of equations are not consistent in the Brinson [Brinson, L.C., 1993. One dimensional constitutive behavior of shape memory alloys: thermomechanical derivation with non-constant material functions and redefined martensite internal variable. J. Intell. Mater. Syst. Struct. 4(2), 229–242.] model, given the assumed form of material functions. In the present work, the nature and implications of the inconsistency are highlighted. The cause of incompatibility is the inconsistent material definitions. A modified consistent constitutive model is proposed by redefining the material function which satisfies the compatibility condition. The advantages in using the proposed modified model are highlighted with numerical case studies involving hysteretic stress–strain behavior.

The use of inverse gas chromatography to assess the acid–base contributions to surface energies of cefditoren pivoxil and methacrylate copolymers and possible links to instability

It is known that acids and bases when mixed together have the potential to react, however, there is complexity when materials are in the solid state, as the surface of the solids may not have all functional groups of the molecule expressed in equal proportions. Conceptually a drug that is acidic when in solution could have a crystal surface that is largely basic (if the acid groups are aligned away from the surface). The interaction of cefditoren pivoxil (a basic drug when dissolved) and various Eudragit polymers was studied. The drug was chemically unstable with Eudragit EPO (basic) and stable with Eudragit L100 or S100 (both acidic). Thus, the hypothesis of this work was that the surface of these materials had a different nature to the dissolved molecules, such that solid state reactions do not proceed in line with the expectation from the solution state. Inverse phase gas chromatography (IGC) was used to investigate the cefditoren pivoxil and the Eudragits. The basic to acidic parameter ratios ( K D/ K A) on the powder surface of the samples by IGC revealed that surface nature was in keeping with the tendency to react, such that the incompatibility could be due to the acid–base interaction between any carbonyl groups having an amphoteric nature on the surface of cefditoren pivoxil crystal and dimethylaminoethyl groups having a basic nature on the powder surface of Eudragit EPO. This study indicated that IGC would be suitable to elucidate the cause of incompatibility between two different solids.

The effect of pH and salt concentration on the coexistence curves of aqueous two-phase systems containing a pH responsive copolymer and polyethylene glycol

The influence of pH and salt concentration on the coexistence curves of aqueous two-phase systems containing a pH responsive copolymer and polyethylene glycol (PEG) is investigated experimentally. The copolymer contains different fractions of anionic polyelectrolyte (APE) and polybetaine (PB) at different pH levels. Compatibility of the two polymers was found to increase with increasing the polyelectrolyte fraction of the copolymer. At high PB content, the copolymer was found to collapse to a very small size under intramolecular electrostatic attractions between opposite charges. The large size asymmetry between the copolymer and the PEG is thought to be the main cause of incompatibility. Salt was found to screen charges and to minimize the influence of pH on compatibility. A two-parameter semi-empirical model was developed, based on the modification of Guan et al. [10] binodal model, to describe the coexistence curve. The model reproduces experimental data accurately. Accuracy of the model was found to increase with increasing size asymmetry of the two polymers.

Reproductive Compatibility, Mating Behavior, and Random Amplified Polymorphic Dna Variability in Some Aphelinus asychis (Hymenoptera: Aphelinidae) Derived from the Old World

Reproductive compatibility, mating behavior, and random amplified polymorphic DNA (RAPID) variability were examined in samples of Aphelinus asychis obtained during foreign exploration for natural enemies of the Russian wheat aphid, Diuraphis noxia (Mordvilko). All specimens were reared initially from Diuraphis sp. collected at several Mediterranean basin localities and 2 localities in Central Asia. Using 7 laboratory cultures, we found 3 reciprocally and completely incompatible groups: the 1st group was represented by a culture from northcentral China, the 2nd group by a Kazakhstani culture, and a 3rd by 5 cultures from the Mediterranean basin (i.e., France, Greece, Morocco, Sicily, and Spain). One instance of partial, 1-way incompatibility was detected among the Mediterranean basin cultures. Behavioral experiments with 3 cultures showed that males respond to the sex pheromone of incompatible females and actively court them. However, females usually did not stop moving or elevate their abdomens in response to courtship by incompatible males. With 1 exception, genital contact and sperm transfer did not occur in incompatible pairings. Thus, rejection of incompatible males or failure to recognize incompatible males by females appeared to be 1 cause of incompatibility. In the exceptional case (Chinese males paired with Kazaklistani females), sperm transfer occurred but at significantly lower frequencies than in control pairings. Phenetic analysis of 61 RAPD loci in 6 laboratory cultures and 3 field samples from the Mediterranean basin delineated the same 3 groups as the compatibility experiment. Further work examining the geographic range, host range, and morphology of the incompatible groups is needed to clarify their taxonomic status.

Effect of Seasonal Changes on Protozoans Inhabiting Artificial Substrates in a Small Pond

Summary A spontaneously occurring dyskinetoplastic Trypanosoma evansi has been observed along with its normal strain. The percentage of dyskinetoplastic form has been found to be increasing in every passage but is eventually eliminated from the circulation. This elimination is due to the competitive exclusion of the mutant strain by the normal strain of T. evansi. Probable cause of incompatibility of this mutant form of T. evansi has been discussed in the light of niche biology of parasite. It is suggested that it may be a case of antibiosis i.e., the existence of the mutant form in the same microhabitat is limited by the normal strain.

Interspecific Incompatibility in Pinus

McWilliam, J. R. (C. S. I. R. O., Canberra, Australia). Interspecific incompatability in Pinus. Amer. Jour. Bot. 46(6): 425–433. Illus. 1959.—The problem of interspecific incompatibility in several intra- and intersectional crosses in the genus Pinus was investigated using both an anatomical and biochemical approach. To provide a background for this work, the development of ovules after intraspecific pollination and of unpollinated ovules was studied. The development of the gametophytes and fertilization after intraspecific pollination in Austrian pine was regular and showed no major deviation from previous descriptions. Unpollinated ovules of Austrian pine broke down approximately 1 mo. after the strobilus became receptive. The break-down appears to result from the lack of some growth factor in the ovule, which in pollinated ovules is probably initiated by the growth of the pollen tube in the nucellus. Parthenocarpy was not observed, nor could it be induced in unpollinated ovules, and it is considered to be a rare phenomenon in the species. The causes of incompatibility in the crosses studied (slash pine × Austrian pine; red pine × pitch pine; Austrian pine × pitch pine; red pine × Austrian pine; Austrian pine × red pine) appear to be related to the inability of the pollen tubes to function normally in the nucellar tissue of a foreign species. Factors that interfere with this normal development indirectly cause the breakdown of the developing gametophyte, and bring about the ultimate collapse of the ovule. In many respects this pattern of development resembles the situation in unpollinated ovules, and again the lack of a specific growth factor appears to be involved. The initial cause of incompatibility following the cross Austrian pine X red pine may be related to a chemical difference between the ovules of these species. Differences found in the concentration of amino acids, particularly arginine, result in a different chemical environment within the ovule. This may interfere with the normal metabolism of the pollen, affecting either its capacity to germinate or its ability to supply the necessary continued stimulus for the development of the gametophyte. Differences in the pattern and timing of the incompatibility reaction following interspecific pollination may reflect the extent of the genetic diversity between the species. In many crosses between species, the incompatibility reaction does not seem to be complete, as evidenced by the vigorous initial pollen tube growth in occasional ovules.

INTERSPECIFIC INCOMPATIBILITY IN PINUS

McWilliam, J. R. (C. S. I. R. O., Canberra, Australia). Interspecific incompatability in Pinus. Amer. Jour. Bot. 46(6): 425–433. Illus. 1959.—The problem of interspecific incompatibility in several intra‐ and intersectional crosses in the genus Pinus was investigated using both an anatomical and biochemical approach. To provide a background for this work, the development of ovules after intraspecific pollination and of unpollinated ovules was studied. The development of the gametophytes and fertilization after intraspecific pollination in Austrian pine was regular and showed no major deviation from previous descriptions. Unpollinated ovules of Austrian pine broke down approximately 1 mo. after the strobilus became receptive. The break‐down appears to result from the lack of some growth factor in the ovule, which in pollinated ovules is probably initiated by the growth of the pollen tube in the nucellus. Parthenocarpy was not observed, nor could it be induced in unpollinated ovules, and it is considered to be a rare phenomenon in the species. The causes of incompatibility in the crosses studied (slash pine × Austrian pine; red pine × pitch pine; Austrian pine × pitch pine; red pine × Austrian pine; Austrian pine × red pine) appear to be related to the inability of the pollen tubes to function normally in the nucellar tissue of a foreign species. Factors that interfere with this normal development indirectly cause the breakdown of the developing gametophyte, and bring about the ultimate collapse of the ovule. In many respects this pattern of development resembles the situation in unpollinated ovules, and again the lack of a specific growth factor appears to be involved. The initial cause of incompatibility following the cross Austrian pine X red pine may be related to a chemical difference between the ovules of these species. Differences found in the concentration of amino acids, particularly arginine, result in a different chemical environment within the ovule. This may interfere with the normal metabolism of the pollen, affecting either its capacity to germinate or its ability to supply the necessary continued stimulus for the development of the gametophyte. Differences in the pattern and timing of the incompatibility reaction following interspecific pollination may reflect the extent of the genetic diversity between the species. In many crosses between species, the incompatibility reaction does not seem to be complete, as evidenced by the vigorous initial pollen tube growth in occasional ovules.

SUPPRESSION OF ISO-AGGLUTININS

Universal donors (group O) are used very commonly for patients belonging to other blood groups. There is a theoretic risk of incompatibility from the use of universal donors whose serum iso-agglutinins are of high titer. Gesse 1 collected forty-six instances of incompatibility resulting in twenty deaths following the use of blood from a universal donor. On the basis of agglutinin titrations he found that more than 30 per cent of universal donors have an agglutinin titer over 1:32, a titer which he considers dangerous. It is obvious that practical experience does not confirm these fears. Vast numbers of transfusions from universal donors are given with complete safety. The rare occurrence of an incompatibility reaction is more apt to be due to inaccurate blood grouping from the use of weak typing serums and weak agglutinogen. Erroneous blood grouping is a more frequent cause of incompatibility. 2 Why can serum containing iso-agglutinins