Evolution of immunoglobulin genes: VH families in the amphibian Xenopus.

We have isolated multiple independent cDNA clones that represent mRNA sequences of immunoglobulin heavy chains from the spleen of adult Xenopus laevis. These cDNA clones contained constant (C) region sequences that were either Cmu or a separate C region sequence believed to be Cnu. In individual cDNA clones the C region sequences were associated with independent heavy-chain variable region (VH) sequences that were classifiable into five distinct families.

IgH enhancer-mediated deregulation of N-myc gene expression in transgenic mice: generation of lymphoid neoplasias that lack c-myc expression.

We have generated transgenic mouse lines that carry one of three different constructs in which the murine N-myc gene is expressed under the control of the immunoglobulin heavy chain transcriptional enhancer element (E mu-N-myc genes). High-level expression of the E mu-N-myc transgenes occurred in lymphoid tissues; correspondingly, many of these E mu-N-myc lines reproducibly developed pre-B- and B-lymphoid malignancies. The E mu-N-myc transgene also appeared to participate in the generation of a T cell malignancy that developed in one E mu-N-myc mouse.

Marrow reticulo-fibroblastoid colonies (CFU-RF derived) spontaneously release an erythroid colony (BFU-E) enhancing factor.

The marrow microenvironment is composed of an extracellular matrix as well as a heterogeneous population of cells. Isolation of the various cell types and analysis of their function is necessary for a better understanding of their roles in hemopoiesis. We have recently reported a colony assay for a cellular component of the marrow microenvironment.

Hemoglobin E: a common hemoglobinopathy among children of Southeast Asian origin.

With the recent immigration of Southeast Asians to Canada, hemoglobin E has become a frequent diagnosis. The clinical and hematologic findings in 42 children (mean age 4.3 years) with hemoglobin E are presented.

Systemic lupus erythematosus and sickle hemoglobinopathies: a report of two cases and review of the literature.

Two adolescent black females with sickle cell disease who developed systemic lupus erythematosus (SLE) are presented. The recognition of SLE was delayed because all new symptoms were initially attributed to their underlying sickle cell disease. Nine similar cases have been previously reported.

Changes in the immune system during metamorphosis of Xenopus.

Profound immunological changes occur as tadpoles metamorphose into adult amphibians. These include the expression of a different antibody repertoire, a lessening of skin graft tolerance, the appearance on leukocytes of class I MHC antigens. Here Martin Flajnik and his colleagues review what is known of these changes in Xenopus and speculate on how they may occur.

Neutrophilic eccrine hidradenitis in acute myelomonocytic leukemia.

Neutrophilic eccrine hidradenitis is a rare but distinct dermatosis that has recently been described in adults with acute myelogenous leukemia. We report the first pediatric case in an 11-year-old girl with acute myelomonocytic leukemia who developed this eruption following her first and second course of VAPA-10 induction chemotherapy. Skin biopsy revealed selective neutrophilic infiltration around the eccrine coils, which is characteristic of this dermatosis.

Major histocompatibility complex-encoded class I molecules are absent in immunologically competent Xenopus before metamorphosis.

The expression of class I and class II major histocompatibility complex (MHC)-encoded antigens has been examined at various stages of the development of the clawed frog, Xenopus. By immunoprecipitation with alloantisera or xenoantisera from radio-labeled spleen and thymus lysates, and by mixed lymphocyte reaction analysis, it was determined that the same class II molecules are expressed throughout ontogeny. In contrast, by fluorescence on frozen sections of tadpoles and by immunoprecipitation, the class I molecule is not detected in tadpoles, but appears on all tissues at the climax of metamorphosis.

Regulation of renal sulfoglycolipid biosynthesis.

The in vitro activity of the renal galactolipid sulfotransferase and the level of sulfated glycolipids in the rat kidney have been correlated as a function of age. The galactolipid sulfotransferase was found to be greatly reduced in the young as compared with the adult animal. The relatively minor changes in the sulfated glycolipid content of the kidney with age suggests that an increase in sulfoglycolipid turnover occurs during growth.

A third immunoglobulin class in amphibians.

A new class of immunoglobulin (IgX) has been found in the South African frog, Xenopus laevis, and other related species. IgX can be immunoprecipitated by monoclonal antibodies directed against determinants found on Xenopus light chain, or on variable regions of heavy chains. Reagents specific for the heavy chain of IgM or the amphibian IgG equivalent, IgY, failed to react with IgX.

Mitogenic effects of phorbol myristate acetate (PMA) on amphibian cells.

Tumour promoter phorbol myristate acetate (PMA) stimulates and causes proliferation of cells from the spleen, thymus and peripheral blood of Xenopus laevis, the clawed toad. Phagocytic cells become activated and from foci of clustered cells. B cells blast and change membrane immunoglobulin (Ig) expression; a small portion go on to secrete Ig.

Anti-IgM treatment influences immunoglobulin heavy and light chain mRNA levels in mitogen-stimulated B lymphocytes.

The mechanism by which soluble anti-IgM inhibits plaque formation by lipopolysaccharide-stimulated B cells was investigated. Since lower amounts of immunoprecipitable mu heavy and kappa light chains were found in cell lysates, this indicated that soluble anti-IgM was inhibiting not only secretion. Subsequently, Northern blot analysis of poly(A+) RNA showed that the steady state levels of mRNA for immunoglobulin heavy and light chain from B cells stimulated with lipopolysaccharide were reduced if the cultures were treated with soluble anti-IgM.

Evaluation of a simple immunodiffusion technique for quantitation of platelet-associated immunoglobulin G in childhood immune thrombocytopenias.

Platelet-associated IgG (PAIgG) was quantitated in 33 children with immune thrombocytopenia and platelet counts less than 100 X 10(9)/liter using a simple radial immunodiffusion (RID) assay. Elevated PAIgG levels were found in 76% (16/21) of children with acute idiopathic thrombocytopenic purpura (ITP), 88% (7/8) of children with chronic ITP, and all four children studied with systemic lupus erythematosus and thrombocytopenia. Normal PAIgG values were found in children with the following disorders: malignancy and chemotherapy-related thrombocytopenia; ITP in remission (platelet counts greater than 150 X 10(9)/liter); various nonimmune hematologic disorders and juvenile rheumatoid arthritis, these children having normal platelet counts.

Studies on Xenopus immunoglobulins using monoclonal antibodies.

Monoclonal antibodies raised against Xenopus Ig recognize antigenic determinants on IgM and low mol. wt Ig (LMW Ig or IgY ). On SDS-PAGE two forms of mu were distinguished in the supernatant and cell lysate of tunicamycin-treated spleen cell culture.

Effector and regulator functions of splenic and thymic lymphocytes in the clawed toad Xenopus.

B cells in Xenopus, as characterized by surface immunoglobulin, nylon-wool adherence and ability to produce antibody in vitro, were found in both major lymphoid organs: 10-25% Ig-positive cells for spleen and 0.5-4% for thymus. The splenic and thymic B cells were able to produce specific antibody of both isotypes, IgM and low molecular weight (LMW) Ig (IgG equivalent).

Immunoglobulin expression in diploid and polyploid interspecies hybrid of Xenopus: evidence for allelic exclusion.

The expression of species-specific surface IgM was studied in various Xenopus species hybrids. Whether the hybrids are diploid or polyploid, a lymphocyte does not produce all of the immunoglobulins (Ig) encloded by the Ig genes present in its genome. This suggests that the selection pressure to make a lymphocyte synthesize only one antibody is high and that allelic exclusion already existed in the ancestors of amphibians which appeared 300 million years ago.

Clinical and laboratory diagnosis of hemostatic disorders in newborn infants.

We describe a microtechnology for the study of the coagulation system in newborn infants. Interpretation of results demands an understanding of the techniques used and the nature of the control population from which normal values are drawn. We have examined two syndromes which represent the majority of hemostatic disorders of sick newborn infants.

Effect of a sputum digestant on the viabiltiy of Mycobacterium fortuitum.

A microcolony technique has been demonstrated as being useful for the rapid determination of the viabilities of single cells of Myocbacterium fortuitum. Cultures of M. fortuitum grown to early logarithmic phase in broth were treated with the sputum digestant N-acetyl-L-cysteine-sodium hydroxide (NALC-NaOH) for periods of 10 to 40 s.