[Pathologic study of circulating blood leukocytes in severe acute respiratory syndrome].
OBJECTIVE
To study the pathologic characteristics and pathogenesis of circulating blood leucocytes infected by severe acute respiratory syndrome associated coronavirus (SARS CoV or SCV) in SARS patients.


METHODS
Blood samples of 22 SARS patients were studied, and 4 healthy blood samples were observed as negative controls. The white blood cells were collected from whole blood. The ultrastructural characteristics were observed by transmission electron microscopy. CD45RO antibody was used for pre-embedding immunoelectron microscopy. The SARS viral sequence was detected with real-time polymerase chain reaction (RT-PCR).


RESULTS
Coronavirus-like particles were founded in the leukocytes in 6 of the 22 blood samples. Five of them gave positive results in the real-time PCR. The number of granulocytes was increased (P < 0.05) and that of lymphocytes was decreased (P < 0.05) respectively. Immunoelectron microscopy showed that CD45RO positive T lymphocyte decreased to 6% - 7%. Circulating lymphocytes had the highest percentage of infection. The morphologic characteristics of coronavirus-like particles were spherical or oval in shape, about 80 - 120 nm in diameter, with a dense round core and a clear halo around the core. A distinct membrane and club-shaped surface projections were seen in the periphery. The particles were located in the cytoplasm, the cisternae of endoplasmic reticulum, Golgi apparatus and vesicles. Virus entered cells by endocytosis or membrane fusion and was released through a budding process.


CONCLUSIONS
Our data suggested that lymphocytes, particularly T cells, were probably the target cells of SARS CoV. The viruses may actively infected the immune cells during SARS CoV acute infection phase and the destruction of target cells may be one of the important reasons for the death of the circulating leukocytes in SARS.
Zhong
Yan-feng
YF
Department of Pathology, Peking University Health Science Center, Beijing 100083, China.
Gao
Xiao-ming
XM
Wang
Sheng-lan
SL
Xie
Zhi-gang
ZG
Ma
Yue
Y
Fang
Wei-gang
WG
Zou
Wan-zhong
WZ
Li
Xiu-lan
XL
Zhang
Qian-ying
QY
Wang
Wei
W
Zhao
Zhen-dong
ZD
Gu
Jiang
J
D005260:Female; D006801:Humans; D007958:Leukocyte Count; D007962:Leukocytes / Q000473:pathology* / Q000648:ultrastructure; D008214:Lymphocytes / Q000473:pathology / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D045169:Severe Acute Respiratory Syndrome / Q000097:blood* / Q000209:etiology / Q000473:pathology