2. Chemical Fab fragment: Fab fragment is a single-arm fragment left after IgG molecules are completely digested by papain to remove Fc fragment and hinge region. It is monovalent, has only one antigen binding site, and its molecular weight is about 50KD. Due to the lack of Fc fragment, antigen cannot be precipitated and cannot be recognized by living immune cells.
However, it has the advantages of small molecular weight and small cross-reaction, so it is often used in functional research in radioimmunoassay, and can also be used to block endogenous immunoglobulins in cells and tissues, and to block IgG antigenic determinants exposed when primary antibodies in multiple immune markers come from the same genus.
3. Leukemia: 1976, blood cell morphological experts from France, the United States and Britain discussed and formulated the diagnostic criteria of acute leukemia, referred to as "FAB" typing.
Extended data:
Etiology of leukemia:
1, virus factor
The effect of RNA virus on leukemia in mice, cats, chickens and cows has been affirmed, and most of the leukemia caused by this virus belongs to T cell type.
2. Chemical factors
Some chemicals can cause leukemia. The incidence of leukemia in people exposed to benzene and its derivatives is higher than that in the general population. It has also been reported that nitrosamines, phenylbutazone and its derivatives, chloramphenicol and so on induce leukemia. Some antineoplastic cytotoxic drugs, such as nitrogen mustard, cyclophosphamide, methylbenzyl hydrazine, VP 16, VM26, etc. , all have leukemia effect.
3. Radiation factors
There is evidence that all kinds of ionizing radiation can cause human leukemia. The occurrence of leukemia depends on the radiation dose absorbed by human body. Leukemia can be induced when the whole body or part of the body is exposed to moderate or large doses of radiation.
Whether low-dose radiation will cause leukemia is uncertain. Frequent exposure to radioactive substances (such as cobalt -60) will significantly increase the incidence of leukemia. High dose radiotherapy will increase the incidence of leukemia.
4. Genetic factors
The incidence of leukemia in people with chromosome aberration is higher than that in normal people.
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