Changes of Canine Peripheral Blood Lymphocytes during the Growth of Transmissible Venereal Tumor Cells

Autor: Shao Wen-Hung, 洪紹文
Rok vydání: 2002
Druh dokumentu: 學位論文 ; thesis
Popis: 90
Canine transmissible venereal tumor ( CTVT ) has been reported worldwide. This low differentiated round cell tumor is transmitted by viable tumor cells through injured mucosa and skin during mating and fighting.. This tumor can be allografted to another dog artificially and mimic a natural condition. Based on the growth status, CTVT is classified into 3 phases, “progressive phase ( P phase ) ”, “stable phase ( S phase ) ” and “regressive phase ( R phase ) ”. The growth and regression of CTVT is believe to be associated with immune responses. It was found in this study that in CTVT laden dogs, the proportions of peripheral blood B lymphocytes ( PBBL ) was decreased. The growth status of the tumor was further divided in to Pb, Pa, Rb and Ra. Pb as early P phase ( from 3 to 8.5 wk post-inoculation, PI), Pa as late P phase ( 10.5 wk to 19 wk PI ), Rb as early R phase ( 19 wk to 22 wk post-inoculation, PI ), and Ra as late R phase ( 22 wk to 25 wk, PI ). It was noted tract the proportion of PBBL gradually decreased from Pb through Ra. The concentrations of both IgG and IgM in dog sera at P and R phase were also gradually decreased during the growth of CTVT and significantly lower that these in the blood before inoculation ( both P < 0.05 ). The supernatants from 48 hr CTVT culture medium also decreased the B cells proportion of PBL. The PBBL depression effect, as further studies by using propidium iodide stain, was caused by the death of PBBL by cell-free cultured medium of CTVT cells and resulted in a decreased proportion of PBBL. This cytotoxicity was specific and did not affect any non-B cells. Therefore, the cytotoxic activities of the CTVT to B-lymphocyte is due to certain toxic substance(s) which is(are) secreted by CTVT and specifically kill PBBL. Because the supernatants lost their abilities to kill PBBL after boiling for 100˚C or treating with protease K, the toxic substance(s) is a protein or bearing a functional protein portion. The molecular weight of the substance(s) was between 30-100 kilo-daltons ( kDa ) and did not carry α-D-mannopyranosyl or α-D-glucopyranosyl residuals. We also found the substance(s) with molecular weight higher than 100 kDa promoted the proliferation of PBBL instead. In the experiment to continue monitoring the change of PBBL after removing all CTVT from a dog, we have found that the dog PBBL proportion requires 22 weeks to recovery from the insult. This further confirm the PBBL depression is due to the growth of CTVT. It may also be one of the mechanisms that CTVT evade host immune surveillance. In this experiment, we found a new lymphocyte subset that expressed CD5lo in peripheral blood lymphocytes ( PBL ). This subset was also depressed in CTVT dogs. The pattern of depression was quite similar to those in PBBL of CTVT dogs. The surface markers of the new immune subset were CD3-, CD4-, CD5lo, CD8+, CD11/18+, CD21-, CD44+, CD45+, DLA ( dog leukocyte antigen ) I + and DLA II+.
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