Interest of simultaneous ultrastructural characterization of morphology, cytochemistry and immune phenotype in a case of putative hybrid acute leukaemia.

A case of acute leukaemia is reported in which blast cells expressed some B-related antigens (namely the CALLA antigen) and no peroxidase activity at the optical level; however, some mature granular cells contained Auer rods. Simultaneous characterization of ultrastructural morphology, cytochemistry and immune phenotype was performed. There was an apparent mutual exclusion in the expression of myeloperoxidase activity and the CALLA antigen, and a heterogeneity in the CALLA expression among the blastic population. These results disagree with the hypothesis of a true biphenotypic leukaemia and demonstrate a complete heterogeneity between the lymphoblastoid cells and the myeloid ones. The interest of such a simple combined method in a case of putative hybrid acute leukaemia is emphasized.

Acute myeloid leukemia with giant inclusions: cytochemical and ultrastructural study.

Giant granules formation was investigated in myeloblasts of a patient with acute myelogenous leukemia by means of the combined techniques of peroxidase cytochemistry both in light and electron microscopy. Several pathologic features were noted: first an abnormal packaging of peroxidase in the peripheral area in large azurophilic granulations, second the progressive enlargement of huge vacuolar inclusions resulting from the interaction and fusion of large azurophilic granules with each other, with normal-sized primary granules and with cytoplasmic components. Microcrystalline structure could not be found in giant vacuoles no in vacuolar inclusions resembling Auer bodies. This last finding could explain that no disseminated intravascular coagulation was observed in our patient.

Serum inhibitory effect on myeloperoxidase in human cancer.

The myeloperoxidase level is strongly depressed in leucocytes from cancer patients (-59%). Moreover sera of the same subjects induce a significant decrease in the myeloperoxidase activity of healthy subjects' leucocytes (-43%). We have found no convincing evidence of any correlation between the level of the inhibitory effect of sera and the tumour type. The fact that sera from cancer patients interfere with neutrophil responses in this way does not exclude the possibility that abnormal cellular functions were also operative.

Relationship between Hassall's corpuscles and thymocytes fate in guinea-pig foetus.

The development and structure of the Hassall's corpuscles are studied with the light and electron microscope in 53 guinea-pig foetuses from 30 to 58 days gestation. The different stages of their life cycle are described. Prior to the appearance of Hassall's corpuscles, no medullary lymphocytes can be found in the early medulla. Hassall's corpuscles are seen initially between 35-42 days gestation. They are surrounded by large and medium-size lymphocytes, while medullary lymphocytes are in close contact with the "external cells" which exhibit cytoplasmic characteristics of a secretory function. The data reported in this paper suggest that Hassall's corpuscles are not the only sites of lymphoid cells destruction but are also "privileged" areas for maturation of medullary lymphocytes at least for the guinea-pig.