Neoplasia de Células Dendríticas Plasmocitoides blásticas: reporte del primer caso en Ecuador / Blastic Plasmacytoid Dendritic Cell Neoplasm : First Case Report in Ecuador

La Neoplasia de Células Dendríticas Plasmocitoides blásticas (Blastic Plasmacytoid dendritic cell neoplasm ­ BPDCN) es una neoplasia hematológica rara, agresiva, de difícil diagnóstico y con alta mortalidad. Se describe el primer caso en el Ecuador de un paciente joven sin antecedentes patológicos relevantes, ingresado al servicio de Medicina Interna del Hospital Enrique Garcés por presentar máculas cutáneas, artralgias y mialgias, que se complica con derrame pleural tipo exudativo y mala mecánica respiratoria. Exámenes de extensión revelaron: Leucemia mieloide aguda de tipo M2, motivo por el cual fue referido a centro oncológico de referencia para completar estudio y manejo. Estudios citogenéticos y fenotípicos corroboraron el diagnóstico de BPDCN, se instauró tratamiento con protocolo Hyper-CVAD, sin embargo, el paciente presentó compromiso respiratorio, renal y hematológico que progresó a choque refractario y óbito. La naturaleza agresiva de esta rara leucemia es una limitante en el tiempo para instaurar un tratamiento dirigido, determinando en la mayoría de los casos una alta mortalidad

La Neoplasia de Células Dendríticas Plasmocitoides blásticas (Blastic Plasmacytoid dendritic cell neoplasm ­ BPDCN) es una neoplasia hematológica rara, agresiva, de difícil diagnóstico y con alta mortalidad. Se describe el primer caso en el Ecuador de un paciente joven sin antecedentes patológicos relevantes, ingresado al servicio de Medicina Interna del Hospital Enrique Garcés por presentar máculas cutáneas, artralgias y mialgias, que se complica con derrame pleural tipo exudativo y mala mecánica respiratoria. Exámenes de extensión revelaron: Leucemia mieloide aguda de tipo M2, motivo por el cual fue referido a centro oncológico de referencia para completar estudio y manejo. Estudios citogenéticos y fenotípicos corroboraron el diagnóstico de BPDCN, se instauró tratamiento con protocolo Hyper-CVAD, sin embargo, el paciente presentó compromiso respiratorio, renal y hematológico que progresó a choque refractario y óbito. La naturaleza agresiva de esta rara leucemia es una limitante en el tiempo para instaurar un tratamiento dirigido, determinando en la mayoría de los casos una alta mortalidad

Flow cytometric immunophenotyping of bone marrow in cats diagnosed with hematopoietic disorders

Cytological examination of bone marrow in cats, due to the large number of cells and various growth phases is somewhat complicated. The use of flow cytometric techniques and monoclonal antibodies are appropriate methods in the diagnosis of hematopoietic malignancies. The purpose of the present study is to determine cell-surface antigens for various developmental stages of feline bone marrow cells in hematopoietic disorders using flow cytometric. In this study, bone marrow cells from 4 cats with hematopoietic disorders and 2 clinically healthy cats, were labeled with 5 types of anti-feline MAbs included: CD21-like [Cr-Br], T lymphocyte subpopulation, CD-172a, Granulocyte, Pan-Leukocyte [CD45-like] and then analyzed using flow cytometric. The results revealed changes in immunophenotyping and light scatter properties compared with normal cases. The percentage of CD45, Granulocyte and CD172a markers in the bone marrow of a cat with erythroleukemia were lower compared with normal bone marrow. In a cat with myelodysplastic syndrome, scatter plot indicated an increase in the immature myeloid cells and a decrease in mature myeloid cells. It was concluded that cytological examination of bone marrow with studying dispersion studies on cells using flow cytometric and usage of a panel of antibodies such as CD21-like[Cr-Br], T lymphocyte subpopulation, CD-172a, Granulocyte, Pan-Leukocyte [CD45-like] could support the diagnosis of feline hematopoietic abnormalities

Prognostic value of [BCLI/IGH] genes juxtaposition and MDRI gene expression in treatment resistant B-NHL

The translocation t[11;14] [q13; q32,] has been known neoplasia for many years found in a variety of B cell malignancies. Through this rearrangement, CCND1/PRAD-1/BCL1 on chromosome 11 becomes juxtaposition to the active immunoglobulin heavy chain [IgH] enhancer on chromosome. MDR1 gene expression lead to overproduction P-gp which leads to chemotherapy resistance caused poor prognosis and short survival [OS and DFS] in B-NHL. To evaluate BCL1/ IgH juxtaposition by FISH and mdr-1 protein expression by immunohistochemistry in B-NHL. To clarify if these genes have some relevance to developing treatment resistance of B-NHL and their correlation with clinical outcome. This is a retrospective study of fifty three bone marrow biopsy samples [fixed and paraffin embedded bone marrow biopsy] for patients with BNHL. In this study t[11;14] detected by FISH was positive in [64.2%] and it was [66. 7%], [64.3%] and [60%] in Mantle cell lymphoma [MCL], Small cell lymphoma [SCL], and Large cell lymphoma [LCL] respectively. The detection frequency of MDR1/ P- glycoprotein [P-gp] by immnunohistochemistry in MCL, SCL and LCL, is [80%], [82%] and [80%] respectively. In this study the frequency of t[11;14] detection by FISH and MDR1/P-gp expression by immnunohistochemistry in our study was consistent with other studies and considered as a marker of diagnostic and poor prognostic for chemotherapy resistance in B-NHL. Presence of both expressions in a patients means very bad prognosis and resistant to chemotherapy. Determining MDR-1/P-gp and t[11;14] in B-NHL is important prior to treatment to allow the design of novel drug regimens containing agent that reverse MDR function

Terapia com células da medula óssea em modelo experimental de insuficiência hepática aguda induzida por acetominofen / Therapy with bone marrow cells in an experimental model of heart failure liver induced by acute acetaminophen

Introdução e objetivos: a insuficiência hepática aguda (IHA), apesar de rara, permanece como uma condição rapidamente progressiva e frequentemente fatal. A intoxicação por acetaminofen (APAP) induz necrose hepática maciça e frequentemente leva à morte por edema cerebral. Terapias celulares são de grande interesse como potenciais tratamentos para IHA. Neste projeto foi avaliado o potencial terapêutico das células mononucleares da medula óssea (CMMO) em um modelo experimental de IHA induzida por APAP em camundongos. Métodos: A IHA foi induzida em camundongos C57Bl/6, previamente submetidos à dieta alcoólica por três semanas, através da administração de APAP na dose de 300 mg/kg por via intraperitoneal. Após a indução da IHA, os camundongos foram transplantados, por via endovenosa, com 107 CMMO...

Introduction and objectives: a cute liver failure (IHA), although rare, remains a rapidly progressive and often fatal condition. Poisoning by acetaminophen (APAP) induces a massive hepatic necrosis and often leads to death by cerebral edema. Cell therapies are of great interest as potential treatments for IHA. In this project we evaluated the therapeutic potential of bone marrow mononuclear cells (BMC) in an experimental model of IHA induced by APAP in mice. Methods: The IHA was induced in C57BL/6 mice previously submitted to the alcohol diet for three weeks by the administration of APAP at a dose of 300 mg / kg, intraperitoneally. After induction of IHA, the mice were transplanted intravenously with 107 BMC...

CD5-negative Blastoid Variant Mantle Cell Lymphoma with Complex CCND1/IGH and MYC Aberrations

The coexistence of CCND1/IGH and MYC rearrangements in mantle cell lymphoma (MCL) is a rare finding associated with a very poor prognosis. In this study, a patient with blastoid variant (MCL) is reported. The disease was clinically aggressive and refractory to chemotherapy, and the patient only survived for 1 month following diagnosis. Conventional cytogenetic study, FISH, and multicolor FISH (mFISH) demonstrated the involvement of the BCL1/CCND1 locus in a complex translocation, t(3;11)(q25;p15)t(11;14)(q13;q32). In addition, subclonal abnormalities in the 8q24 region, manifested as a t(8;14)(q24;q32)/MYC rearrangement, were identified. To the best of our knowledge, this is the first MCL case in Korea bearing these complex genomic aberrations.

Prolonged expression of MHC class I - peptide expression in bone marrow derived retrovirus transfected matured dendritic cells by continuous centrifugation in the presence of IL-4.

Background & objectives: Dendritic cells (DCs) are potent antigen presenting cells which proceed from immature to a mature stage during their differentiation. There are several methods of obtaining long lasting mature antigen expressing DCs and different methods show different levels of antigen expressions. We investigated bone marrow derived DCs for the degree of maturation and genetically engineered antigen presentation in the presence of interleukin-4 (IL-4) as a maturity enhancer. Methods: DCs and transfected retrovirus were cultured together in the presence of granulocyte-macrophage colony stimulating factor (GMCSF)-IL4, GMCSF +IL4, lipopolysaccharide (LPS). B 7.1, B7.2 and CD11c were measured by the degree of immune fluorescence using enhanced green fluorescent protein (EGFP) shuttled retrovirus transfected antigen. Degree of MHC class I molecule with antigen presentation of antigen was also evaluated by fluorescence activated cell sorting. The antigen presenting capacity of transfected DCs was investigated. Bone marrow DCs were generated in the presence of GMCSF and IL-4 in vitro. Dividing bone marrow cells were infected with EGFP shuttled retrovirus expressing SSP2 by prolonged centrifugation for three consecutive days from day 5, 6 and 7 and continued to culture in the presence of GMSCF and IL-4 until day 8. Results: IL-4 as a cytokine increased the maturation of retrovirus transfected DCs by high expression of B 7-1 and B 7-2. Also, IL-4 induced DC enhanced by the prolonged centrifugation and it was shown by increased antigen presentation of these dendric cells as antigen presenting cell (APC). Cytolytic effects were significantly higher in cytotoxic T cell response (CTLs) mixed with transfected DCs than CTLs mixed with pulsed DCs. Interpretation & conclusions: There was an enhanced antigen presentation by prolonged expression of antigen loaded MHC class I receptors in DCs in the presence of IL-4 by prolonged centrifugation.

Estudio del polimorfismo genético de las células de la médula ósea y del sistema nervioso central de ratas mediante la técnica de RAPD / Study of genetic polymorphism of the bone marrow and the central nervous system of rats cells by RAPD technique

Los modelos experimentales en rata han sido de gran utilidad en las evaluaciones terapéuticas o de reemplazo de células en enfermedades neurodegenerativas. Se ha comprobado que las células de la médula ósea (CMO) de ratas pueden diferenciarse en células que no forman parte de sus linajes normales. Hay evidencias de estos procesos de trans-diferenciación, pero aún no se conocen los mecanismos moleculares que activan estos procesos. El propósito de nuestro trabajo fue estudiar el polimorfismo genético del ADN de los tipos celulares que conforman las CMO y las células del sistema nervioso central (SNC), estríatales y de la corteza de ratas mediante la técnica de RAPD. Las CMO, las células mononucleares (CMMO), las células estromales (CEMO) y las del SNC fueron obtenidas de ratas, y su ADN genómico fue purificado y amplificado mediante la técnica de RAPD, utilizando 15 cebadores al azar. Se construyó un dendograma de las bandas de amplificación generadas utilizando el método de UPGMA. Las células estudiadas según el análisis del RAPD quedaron en 2 grupos bien definidos, pudiéndose diferenciar las CEMO del resto de las células estudiadas. Los cebadores OPA-6, 7 y 12, mostraron el polimorfismo genético de los linajes de células estudiadas. Mediante la técnica de RAPD se demostró la variabilidad genética entre las CEMO y las CMMO, células estriadas y de corteza que mostraron una homogeneidad genética, proponiéndose marcadores específicos de RAPD para cada grupo de células. Este es el primer estudio del polimorfismo genético de las CMO y del SNC de ratas.

Experimental models have been of grate usefulness in the therapeutic or replacement cells in neurodegenerative diseases. It has been demonstrated that bone marrow cells (BMC), can be difefferentiated in cells that do not form part of their normal lineage. There is evidence of these trans-differentiation processes in these cells, but nevertheless, molecular mechanisms that activate these differentiation process still not known. The purpose of our work was to study the genetic polymorphism of those cellular types; that conform the rat bone marrow cells (BMC) as well as those of the central nervous system (CNS), striatum cells and cortex ones, trough RAPD technique. BM, mononuclear cells (BMMC), estromal cells (BMSC) and the CNS cells were obtained from rats and genomic ADN was purified and amplified through RAPD technique, using 15 random primers. A dendogram was constructed according to UPGMA method of the amplifying RAPD bands. Studied cells as- according to the RAPD analysis- were grouped into 2 well- defined groups, as CEMO coud be differentiated from the rest of studied cells. OPA-6, 7 and 12 primers showed the genetic polymorphism of the studied lineages cells. Also will be proposed specific RAPD genetic markers. Through RAPD technique permitted the genetic variability was demonstrated betwen BMEC and BMMC of striated cells and of cortex, which demonstratd a genetic homogeneity through RAPD technique so specific genetic markers of RAPD were thus propose for each group of cells. These constitute the first study on genetic polymorphism of BMC and CNS.

Immunophenotyping of mature T/NK cell neoplasm presenting as leukemia.

Introduction : Mature T/NK cell lymphomas (MTNKL) presenting as leukemia are rare and show considerable overlapping of clinical, morphological and immunophenotypic features. AIM: Critical analysis of the morphology and immunophenotypic profile of MTNKL. Materials and Methods : We reviewed 380 consecutive cases of mature lymphoid neoplasm that presented as leukemia and were diagnosed on morphology and immunophenotyping of bone marrow and/or peripheral blood samples. Results : Peripheral blood and bone marrow involvement was seen in all cases. MTNKL constituted 4% (nine cases) of all mature lymphoid neoplasms presenting as leukemia. It included four cases of T-large granular leukemia (T-LGL), two of T-cell prolymphocytic leukemia small cell variant (T-PLL), two of adult T-cell leukemia/lymphoma (ATLL) and one of primary cutaneous gamma delta T-cell lymphoma (PCGDTCL). T-LGL revealed CD4-/CD8+ phenotype in three, and CD4+/CD8+ phenotype in one case. CD56 was absent in all the cases of T-LGL. One case of T- PLL small cell variant showed CD4+/CD8- phenotype, while the other revealed CD4-/CD8+ phenotype. Both cases of ATLL showed CD4+/CD8+/CD25+ phenotype. The single case of PCGDTCL showed CD4-/CD8- phenotype pattern. CD3 and CD5 were expressed in all MTNKL. CD7 was absent in three cases of T-LGL. TCRα/β was performed in three cases of T-LGL and was positive in all. TCRα/β was also seen in both the cases of T-PLL small variant. However, TCRα/β was seen in the single case of PCGDTCL. Conclusion : Mature nodal T/NK cell neoplasms are rare and MTNKL presenting as leukemia are even rarer. There is an overlap between the immunophenotypic profiles of different MTNKL subtypes and elaborate T/NK cell panels are required for their evaluation.

Concurrent Langerhans Cell Histiocytosis and B-Lineage Lymphoid Proliferation in the Bone Marrow / 대한진단검사의학회지

We present three cases of concurrent Langerhans cell histiocytosis (LCH) and B-lineage lymphoid cell infiltrations and/or nodules in the bone marrow. The first patient was a 25-month-old boy who presented with LCH on the right shoulder and multiple osteolytic lesions. Bone marrow biopsy showed the presence of LCH and two large lymphoid nodules of B-lineage, which were located in the paratrabecular region. Both LCH and the lymphoid nodules resolved after treatment with prednisone, vinblastine, methotrexate, and cyclophosphamide. The second patient was a 7-month-old girl who presented with LCH in the scalp and bone marrow. In spite of the treatment, a follow-up bone marrow analysis performed after 16 months showed LCH and increased B-lineage lymphoid cells in the interstitial area. The third patient was a 26-month-old girl, and imaging studies revealed reddish skin lesions and multiple osteolytic lesions. Skin biopsy and bone marrow biopsy did not show the presence of LCH; however, we initiated the treatment on the basis of the results of imaging studies. The follow-up study after 6 months showed the presence of LCH and large, patchy infiltration of B-lymphoid cells. We report three rare cases of concurrent bone marrow involvement of LCH and B-lineage lymphoid proliferation, which strongly suggest lymphoid malignancy. Further, clonal changes should be studied to elucidate the common pathogenic mechanism between the two diseases.

Clinically unsuspected Hodgkin's lymphoma diagnosed primarily from bone marrow trephine biopsy: report of six cases.

Bone marrow may be the initial or rarely the only site of involvement in Hodgkin's lymphoma. A high index of suspicion is required to pick up the histopathological changes of Hodgkin's lesions in the bone marrow like necrosis, presence of Reed-Sternberg cell or its variant in a polymorphic background infiltrate, focal fibrosis and myxoid change especially in the absence of classical clinical picture. Bone marrow with immunohistochemistry has a valuable role in the staging and in the diagnosis of primary medullary Hodgkin's lymphoma. B-symptoms may easily masquerade as an infectious process as in all our cases the patients had fever as a presenting feature, in four of them tuberculosis was suspected clinically and two had received antitubercular therapy elsewhere. We report six human immunodeficiency virus-negative patients diagnosed over a period of 5 years in which the initial diagnosis of Hodgkin's lymphoma was suggested from bone marrow histology.

Asynchronous expression of myeloid antigens in leukemic cells in a PML/RARalpha transgenic mouse model

Acute promyelocytic leukemia (APL) is characterized by the expansion of blasts that resemble morphologically promyelocytes and harbor a chromosomal translocation involving the retinoic acid receptor a (RARa) and the promyelocytic leukemia (PML) genes on chromosomes 17 and 15, respectively. The expression of the PML/RARa fusion gene is essential for APL genesis. In fact, transgenic mice (TM) expressing PML/RARa develop a form of leukemia that mimics the hematological findings of human APL. Leukemia is diagnosed after a long latency (approximately 12 months) during which no hematological abnormality is detected in peripheral blood (pre-leukemic phase). In humans, immunophenotypic analysis of APL blasts revealed distinct features; however, the precise immunophenotype of leukemic cells in the TM model has not been established. Our aim was to characterize the expression of myeloid antigens by leukemic cells from hCG-PML/RARa TM. In this study, TM (N = 12) developed leukemia at the mean age of 13.1 months. Morphological analysis of bone marrow revealed an increase of the percentage of immature myeloid cells in leukemic TM compared to pre-leukemic TM and wild-type controls (48.63 ± 16.68, 10.83 ± 8.11, 7.4 ± 5.46 percent, respectively; P < 0.05). Flow cytometry analysis of bone marrow and spleen from leukemic TM identified the asynchronous co-expression of CD34, CD117, and CD11b. This abnormal phenotype was rarely detected prior to the diagnosis of leukemia and was present at similar frequencies in hematologically normal TM and wild-type controls of different ages. The present results demonstrate that, similarly to human APL, leukemic cells from hCG-PML/RARa TM present a specific immunophenotype.

Vacunación en huéspedes inmunocomprometidos / Vaccine in immunocompromiced host

Los lactantes, niños y adolescentes con inmunodeficiencia primaria o secundaria constituyen una población creciente. La adecuada utilización de las vacunas incluídas en el Calendario Nacional y otras son una valiosa herramienta para la calidad de vida. Debe considerarse simultáneamente la vacunación de los convivientes. La indicación de la vacuna es personalizada. Se revisan las indicaciones en los pacientes con tratamiento prolongado con corticoides; inmundeficiencia primaria (humoral, celular/combinada); inmunodeficiencia secundaria (cáncer, transplante médula ósea/órganos sólidos.)

Acute myeloblastic leukemia in a patient with primary antiphospholipid syndrome

Antiphospholipid syndrome is characterized by venous and arterial thrombosis, recurrent pregnancy loss and the presence of the lupus anticoagulant, anticardiolipin antibodies or both. Antiphospholipid syndrome may occur as a primary disease or in patients with systemic lupus erythematosus or other autoimmune, infectious or neoplastic disorders. In this paper we report a 29-year-old Saudi female, a known case of antiphospholipid syndrome, presented with complaints of fever, breathlessness and generalized fatigue. Further investigations confirmed her as a case of myeloblastic leukemia [M1, French-American-British classification]. Acute myeloblastic leukemia is not described to be associated with primary antiphospholipid syndrome in the literature to date. This is the first case report of such association

Síndrome de kostmann: presentación de un caso / Kostmann syndrome: presentation of a case

El síndrome de Kostmann o agranulocitosis congénita infantil es un trastorno inmunológico hereditario caracterizado por una disminución severa del valor absoluto de neutrófilos; así como la aparición de infecciones piogénas recurrentes en los primeros años de vida. Se describe el caso de un lactante menor masculino de 7 meses de edad, quien ingresa al Hospital de Niños "J.M. de Los Ríos" por presentar fiebre, infección pulmonar y neutropenia. El diagnóstico de síndrome de Kostmann o agranulocitosis congénita se basa por los hallazgos en el aspirado y la biopsia de médula; y el tratamiento con factor estimulante de colonias granulocíticas evitó nuevas infecciones bacterianas

Comparison of CD34+ subsets and clonogenicity in human bone marrow, granulocyte colony-stimulating factor-mobilized peripheral blood, and cord blood

To compare the clonogenicity and distribution of CD34+ subsets in bone marrow (BM), granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood (PB) and cord blood (CB), we analyzed in vitro colony formation and CD34+ cells co-expressing differentiation molecules (CD38, HLA-DR), myeloid associated molecules (CD13, CD33), a T-cell associated molecule (CD3), and a B-cell associated molecule (CD19) from mononuclear cells (MNCs) in the three compartments. The proportions of CD34+CD38- cells (BM: 4.4+/-2.8%, PB: 5.3+/-2.1%, CB: 5.9+/-3.9%) and CD34+HLA-DR cells (BM: 4.7+/-3.4%, PB: 5.5+/-2.3%, CB: 6.1+/-3.7%) did not differ significantly among the compartments. In contrast, a significantly higher proportion of CD34 cells of PB and CB co-expressed CD13 (75.0+/-11.4%, 77.7+/-17.3%) and CD33 (67.1 +/-5.7%, 56.8+/-10.3%) compared with those of BM (43.0+/-6.3%, 27.6+/-5.1%) and a significantly higher number of granulocyte-macrophage colony-forming units (CFU-GM) and erythroid burst-forming units (BFU-E) were detected in MNCs derived from PB and CB compared with those from BM (p<0.01). The proportion of CD34+CD19+ cells was higher in BM (34.9+/-11.9%) than those in PB (5.6+/-3.0%) and CB (4.7=2.1%) (p<0.05). The proportion of CD34+CD3+ was comparable in all three compartments. In conclusion, our findings show that MNCs of mobilized PB and CB display similar phenotypic profiles of CD34+ subsets and clonogenicity, different from those of BM.

CD34 immunohistochemical staining of bone marrow biopsies in myelodysplastic syndromes

Although it has been shown that the percentage of bone marrow blasts in myelodysplastic syndrome (MDS) constitute the only independent determinant of survival and progression to acute leukemia, the great variability in survival among patients with MDS of similar percentage of blasts has prompted us to investigate new objective, independent prognostic parameters for the selection of high-risk patients. It was suggested that CD34 antigen expression adversely affected the prognosis of acute myelogenous leukemia. However, no study has been published so far on clinical and prognostic significance of CD34 antigen expression in MDS. Bone marrow biopsies from 58 patients diagnosed as primary MDS were studied using QBEND/10, a monoclonal antibody which recognized the human progenitor CD34 antigen on routine aldehyde-fixed, paraffin-embedded samples. The high percentage of CD34-positive cells (above 3% of total bone marrow nucleated cells) was predominantly observed in cases with RAEB-T, CMML, and to a lesser degree in RAEB. But neither age, hemograms, bone marrow findings including percentage of blasts, ALIP, nor leukemic transformation correlated with the percentage of CD34-positive cells. The median actuarial survival time in the high positive group was significantly shorter (12.0 months) than that of the low group (30.0 months; p = 0.028). The high CD34 aggregate (> or = 3) was selectively found in cases with RAEB, RAEB-T, and CMML. The percentage of bone marrow blasts (p = 0.007) and ALIP (p = 0.030) significantly correlated with number of CD34 aggregates.

Differential expression of leukocyte common antigen in human fetal lymphoid organs

To investigate the differential expression of various types of leukocyte common antigen (LCA) isoforms during development, we analyzed human fetal lymphoid organs, including the thymus, liver, spleen, and bone marrow from 14 weeks to 29 weeks of gestational age by immunohistochemical and flow cytometric methods. In fetal thymus, over 90% of thymocytes throughout the entire fetal life expressed CD45RO and CD45RB, while CD45RA was expressed only in less than 5% of thymocytes. This expression pattern of LCA isoforms was established by a gestational age of 14 weeks or earlier, and persisted throughout the fetal period. The tissue distribution was different from each isoform; CD45RO-positive thymocytes were found in both the cortex and medulla at the 14th week with low intensity, but was localized in the cortex with increasing fetal age. CD45RB-positive thymocytes distributed mainly in the medulla from early gestational age. Among extrathymic lymphoid organs, a small portion of lymphoid cells expressing leukocyte common antigens appeared first in the liver at 10-12 weeks of gestational age and was followed by a small number in the spleen and bone marrow by 13-15 weeks. All lymphoid cells in these extrathymic lymphoid organs at this stage were CD19+ B cells. The number of these CD19+ cells increased abruptly during the early period of mid-gestational age. The pattern of tissue distribution of each LCA isoform in the fetal liver and spleen correlated well with the patterns of quantitative analysis by flow cytometry. In summary we found that different LCA isoforms expressed in cell-type-specific pattern and showed different tissue distribution during the period of fetal development, and that LCA was the earliest antigen expressed by lymphocytes in the thymus and extrathymic lymphoid organs in our series.

Studies on the pathogenesis of aplastic anemia in Thailand: evidence of immune-mediated mechanism.

The pathogenesis of aplastic anemia in Thailand was studied by using in vitro progenitor cells culture. In 37 patients who had active disease, the numbers of colonies derived from erythroid and granulocyte-macrophage progenitor cells (BFU-E and CFU-GM) were markedly decreased both in the blood and bone marrow as compared to normal controls. Co-culture of patients' cells with normal blood cells was performed in order to verify an immunologically mediated mechanism. In 8 of 26 patients, there were very low numbers of colonies both BFU-E and CFU-GM in the blood and bone marrow with significant suppression of colony formation in co-culture. Suppressor cells may have caused the aplasia in these patients. The rest had low colony formation and no suppression in co-culture. These patients may have absent or defective stem cells. None had normal colony formation. Therefore, aplastic anemia in Thailand may result mostly from defects involving the stem cells. Only some patients had cell mediated suppression of hematopoiesis as detected by co-culture.