Cold hemagglutinin cross-reactivity with Mycoplasma pneumoniae

Mycoplasma pneumoniae: A Potentially Severe Infection

Mycoplasma pneumoniae infections remain one of the most common etiologies of community-acquired pneumonia (CAP). The clinical presentation and manifestations vary widely and can affect all organs of the body. Diagnosis is challenging because there are no constant findings in physical exams or laboratory or radiological assessments that indicate Mycoplasma pneumoniae pneumonia, and specific diagnostic tools are not readily available. Extrapulmonary manifestations and severe pulmonary manifestations can lead to long-term sequelae. The increasing emergence of Mycoplasma pneumoniae that is resistant to macrolides in some areas of the world and increased world travel could add to the difficulty of controlling and treating Mycoplasma pneumoniae infections. We present a concise and up-to-date review of the current knowledge of Mycoplasma pneumoniae pneumonia.

An interesting case of mycoplasma pneumonia associated multisystem involvement and diffuse alveolar hemorrhage

Severe mycoplasma pneumonia is a rare entity with only 0.5–2% of cases having a fulminant course. We present a 74-year-old woman with hypertension, diabetes mellitus and remote history of marginal zone B-cell lymphoma admitted with abdominal pain and diarrhea of 1–2 days associated with body-aches, dyspnea, dry cough and weight loss for 2–3 weeks. On physical exam, she was febrile, tachypneic, tachycardic and hypoxic on room air. Chest examination revealed diffuse crackles and end-expiratory wheezes. Laboratory tests showed anemia, acute-on-chronic kidney injury and hyaline casts and epithelial cells in the urine analysis. Chest roentgenogram and computed tomograhphy scan showed pulmonary infiltrates. Intravenous ceftriaxone and azithromycin with bronchodilators were initiated. Her clinical course was complicated by hypoxic respiratory failure, hemoptysis, and worsening of infiltrates, requiring intubation and mechanical ventilation. Bronchoscopic bronchoalveolar lavage was consistent with diffuse alveolar hemorrhage (DAH). The patient's serum was positive for IgM antibody to Mycoplasma pneumoniae [1134 U/mL] and Anti-I-specific IgM-cold-agglutining [1:40]. A diagnosis of severe mycoplasma infection with DAH was made. The patient was treated with an additional course of doxycycline, pulse dose steroids and plasmapharesis with good clinical response. Surgical lung biopsy showed focal acute lung injury. Bone marrow biopsy and fat pad biopsy were normal. She was liberated from mechanical ventilation and discharged. She returned within 24 hours of discharge with cardiac arrest and new onset right-bundle-branch-block. We hypothesize our patient had severe mycoplasma pneumonia with DAH and multisystem complications of the same including a possible venous thrombo-embolic episode leading to her demise.

Transient cold agglutinins associated with Mycoplasma cynos pneumonia in a dog

This report details a case of reversible cold agglutinins in a dog with Mycoplasma cynos pneumonia. An 11-month-old female spayed Rhodesian Ridgeback was presented for lethargy and cough. Thoracic radiographs revealed an alveolar pattern present bilaterally in the cranioventral lung lobes. Septic neutrophilic inflammation with suspected Mycoplasma sp. organisms was noted on cytologic examination of a trans-tracheal wash, and the dog was treated empirically with IV ampicillin/sulbactam and enrofloxacin pending culture results. Red blood cell agglutination was noted unexpectedly on several blood film reviews during hospitalization; however, the dog never developed clinical or laboratory evidence of hemolysis. Cold agglutinins were demonstrated based on the results of a saline dilution and cold agglutinin test that showed agglutination at 4°C but not at room temperature (21°C) or 37°C. Based on a positive culture for M cynos, the dog was treated for 8 weeks with oral enrofloxacin. After clinical and radiographic resolution of the pneumonia, repeated saline dilution and cold agglutinin tests of peripheral blood were negative at all temperatures. Reversible, asymptomatic cold agglutinins are common in human patients with mycoplasma pneumonia, but this is the first reported case in a dog.

Bystander Immune Cytolysis

In addition to alloimmune and autoimmune cell lysis, a third category of immune destruction of blood cells should be recognized. This additional immunologic response occurs when cells or tissues are injured by immunologic reactions in which the cells act as "innocent bystanders." One mechanism by which an immune response to an exogenous antigen leads to the destruction of autologous blood cells is the temporary development of autoantibodies. This is actually an alloimmune reaction which results in a temporary state of "pseudo"-autoimmunity. Although originally described as a type of hemolysis of autologous cells, the concept of bystander immune cytolysis has been extended to include other instances in which immune destruction of cells is caused by antibody that is not developed in response to intrinsic antigens on the cell being lysed. In recent years, compelling data have been presented documenting bystander immune cytolysis in a number of different clinical settings, and efforts have been made to define the mechanisms by which this occurs. Physicians must be aware that some examples of immune lysis of autologous cells are, in reality, examples of temporary bystander immune cytolysis rather than true autoimmune disease. Furthermore, some alloimmune hemolytic reactions can result in lysis of bystander cells.

IL-10 and the Cytokine Network in the Pathogenesis of Human Autoimmune Hemolytic Anemia

In animal and human autoimmune hemolytic anemia (AIHA) immunologic tolerance loss against RBC self-antigens could be originated by several mechanisms: ignored self-antigens' epitopes, polyclonal lymphocyte activation, molecular mimicry between self- and foreign antigens, central or peripheral tolerance errors, or immunoregulatory disturbances including the alteration of a cytokine network. To identify the immunologic factors contributing to autoimmune onset and maintenance, several murine strains (such as NZB and NZB/NZW) that spontaneously develop a complex autoimmune syndrome, including AIHA, have been extensively studied. In human AIHA, the respective roles of IL-2, IL-4, IFN-gamma, IL-10, and IL-12 were investigated by examining the spontaneous and mitogen-induced (OKT3 or LPS) production of these cytokines. ELISA methods were used in PBMCs to evaluate whether the manipulation of IL-10/IL-12 balance can have an effect on the incidence of autoimmune diseases and whether this might be useful for the control of AIHA. Results affirmed that AIHA is a disease that exhibits an increased basal synthesis of IL-4 and decreased levels of IFN-gamma by AIHA PBMCs compared with controls and that there is a basal increase of Th2 cytokines. Th1-type cytokine decrease in the basal state occurred in parallel with an increase of constitutive IL-10 production and an IL-12 decrease. In conclusion, decreased production of Th1-type cytokines and the production of autoantibodies in AIHA may be secondary to the imbalance between IL-10 and IL-12, and the neutralization of IL-10 may be efficacious in diminishing the clinical pathology associated with Th2 subset prevalence. In the same way, the treatment with IL-12 could offer a second and independent level of blockade against the consequences of the overstimulation of B cells associated with AIHA.

Immunological tolerance loss vs. erythrocyte self antigens and cytokine network disregulation in autoimmune hemolytic anaemia

Recent studies on animal and human autoimmune hemolytic anaemia (AIHA) suggest that the loss of immunological tolerance vs. erythrocyte (Er) self antigens (Ag) may be primed by different mechanisms: ignorance of Er self Ag, molecular mimicry between self and non-self Ag, polyclonal T and/or B cells activation, errors in central or peripheral tolerance, immunoregulatory disturbances including the alteration of cytokines network. In vitro stimulation by synthetic Rh peptides indicates that ignorant T and/or B cells from patients with AIHA may recognize criptic Er self Ag. The AIHA associated with bacterial or viral infections seems to be produced by polyclonal T and/or B cell activation against foreign Ag that mimics protein or carbohydrate epitopes on Er. Polyclonal activation of host B cell clones by donor T cells causes the AIHA in chronic graft-versus-host disease. Mouse lines expressing a transgene with autoantibody (autoAb) activity against murine Er have shown that non-deleted peripheral B cell clones may produce Er autoAb. In human a genetic defect of Fas/FasL autoreactive lymphocyte apoptosis may be associated with AIHA. Th1/Th2 cytokines or IL10/IL12 imbalance may induce AIHA: in NZB mice and in human AIHA there is an increased production of Th2 cytokines such as IL4 and IL10 but INF-gamma and IL12 reduced production. Particularly, IL10 seems to act as critical mediator for the Er autoAb production.

Mechanisms of immunological tolerance loss versus erythrocyte self-antigens and autoimmune hemolytic anemia

Recent studies on animal and human autoimmune hemolytic anemia (AIHA) suggest that immunological tolerance loss toward red blood cells (RBC) self-antigens may be originate by different, non-mutually exclusive, mechanisms. According to now available data the identified mechanisms may be: ignorance against RBC self-antigens; molecular mimicry; polyclonal T and/or B cells activation; errors in central or peripheral tolerance; immunoregulatory disorders including cytokine network alteration. In some patients with AIHA, stimulation of PMBC by synthetic Rh peptides indicate that ignorant T and/or B cell clones may recognize cryptic RBC self-antigens. AIHA associated with bacterial or viral infections seems to be produced by polyclonal T and/or B cells activation against foreign antigens which mimic protein or carbohydrate epitopes on RBC. Polyclonal activation of host B cell clones by donor alloreactive T cells causes the AIHA in chronic GVHD. As the tolerance loss is concerned, experiments on mouse lines expressing a transgene with autoantibody activity against murine RBC have shown that non-deleted peripheral B cell clones may produce RBC autoantibodies. In humans a genetic defect of Fas/FasL autoreactive lymphocytes apoptosis may be associated to AIHA. Immunoregulatory disorders due to depletion of CD4+ CD25+ T cells or Th1/Th2 cytokines imbalance may induce autoimmune diseases. In mice AIHA may be induced or improved by cytokines or anticytokine antibodies administration. In NZB/W mice and human AIHA there is an increased production of Th2 cytokines as IL4 and IL10 but INF-gamma reduced production. In addition in human AIHA has been shown a downregulation of IL12 and therefore, an IL10/IL12 immunoregulatory circuit imbalance which might facilitate the RBC autoantibodies production.

Transgenic B lymphocytes expressing a human cold agglutinin escape tolerance following experimental infection of mice by Mycoplasma pulmonis

Several microbial infections, including Mycoplasma pneumoniae respiratory infection, are capable, in man, of transiently inducing the expression of anti-red blood cell autoantibody called cold agglutinins (CA). To analyze the mechanisms by which immune tolerance is broken following a mycoplasma infection, we used transgenic mice expressing a pathogenic human CA, designated CA-GAS, specific for sialylated carbohydrates. In these mice peripheral deletion of autoreactive B lymphocytes and receptor editing, prevent the development of autoimmune hemolytic anemia. Experimental infections of transgenic mice with Mycoplasma pulmonis resulted in a high anti-mycoplasma antibody response (despite a severe B cell depletion at the onset of infection), and an important induction of serum CA concentrations, reaching in some mice pathological titers. Whereas in naïve mice, only a small percentage of CA-expressing cells could be detected, in infected mice, a majority of circulating B lymphocytes were large B220(-) cells, which expressed the transgenic immunoglobulin. Immunization of the transgenic mice with keyhole limpet hemocyanin and Freund's adjuvant, to nonspecifically stimulate the expression of the passenger transgenes, only moderately increased the CA titers. These results indicate that M. pulmonis infection is capable of breaking immune tolerance in the CA-transgenic mice, in part through specific activation of CA-expressing B lymphocytes. This experimental infection mimics the induction of CA in humans and provide an animal model for studying the genesis of the autoimmune hemolytic anemia.

Three-dimensional structure of the Fab from a human IgM cold agglutinin

Cold agglutinins (CAs) are IgM autoantibodies characterized by their ability to agglutinate in vitro RBC at low temperatures. These autoantibodies cause hemolytic anemia in patients with CA disease. Many diverse Ags are recognized by CAs, most frequently those belonging to the I/i system. These are oligosaccharides composed of repeated units of N:-acetyllactosamine, expressed on RBC. The three-dimensional structure of the Fab of KAU, a human monoclonal IgM CA with anti-I activity, was determined. The KAU combining site shows an extended cavity and a neighboring pocket. Residues from the hypervariable loops V(H)CDR3, V(L)CDR1, and V(L)CDR3 form the cavity, whereas the small pocket is defined essentially by residues from the hypervariable loops V(H)CDR1 and V(H)CDR2. This fact could explain the V(H)4-34 germline gene restriction among CA. The KAU combining site topography is consistent with one that binds a polysaccharide. The combining site overall dimensions are 15 A wide and 24 A long. Conservation of key binding site residues among anti-I/i CAs indicates that this is a common feature of this family of autoantibodies. We also describe the first high resolution structure of the human IgM C(H)1:C(L) domain. The structural analysis shows that the C(H)1-C(L) interface is mainly conserved during the isotype switch process from IgM to IgG1.

Peripheral neuropathy in cold agglutinin disease

Cold agglutinin disease (CAD) characteristically presents as anemia and cold-induced rash. We report a man with purpura, anemia, cold agglutinins, and a sensory-autonomic polyneuropathy. Treatment with corticosteroids and plasma exchange resulted in resolution of the anemia and polyneuropathy. We propose that CAD may be associated with a reversible sensory-autonomic neuropathy in the absence of cryoglobulinemia. Although unsupported by pathologic findings, pathogenetic hypotheses for the neuropathy in CAD are similar to those proposed for cryoglobulinemic neuropathy.

Detection of antibodies against membrane-glycoproteins of swine erythrocytes after experimental infection with Mycoplasma hyopneumoniae

During enzootic pneumonia of pig, antibodies against membrane glycoproteins of erythrocytes were detected with an enzyme-linked immunosorbent assay (ELISA). These antibodies arise simultaneously with the specific antibodies. They are not identical to cold agglutinins.

Cold agglutinins accompanying Mycoplasma pneumoniae infection

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Immune electron microscopy of cross-reactions between Mycoplasma pneumoniae and human erythrocytes

Respiratory infection with Mycoplasma pneumoniae evokes immunoglobulin M autoantibody which agglutinates human erythrocytes at 4 degrees C (cold agglutinin) and is specific for I antigen. Cross-reactions between surface antigens of M. pneumoniae and human erythrocytes, previously examined by serological analysis, were examined by transmission and scanning electron microscopy. Ferritin-labeled human antimycoplasmal and rabbit antisera to erythrocyte membrane components reacted with antigens on the surface of both M. pneumoniae and erythrocytes. Adsorption of human erythrocytes to M. pneumoniae was blocked by the same antisera without ferritin label. It is proposed that the cross-reactive specificity lies in peripheral areas of the mycoplasmal cell, probably in a surface carbohydrate which has antigenic identity with erythrocyte glycoprotein.