van Nie R, de Moes J
Int J Cancer. 1977 Oct 15;20(4):588-94. doi: 10.1002/ijc.2910200417.
Based on the previous observation that Mtv-2 controls the appearance of pregnancy-dependent mammary tumours and the early expression of mammary tumour virus (MTV)-antigens in the milk, an attempt was made to develop a congeneic GR line, without this locus, by introducing genetic material of the C57BL/10 strain. The cross-intercross system was used for this purpose. The mice of the even-numbered generations were selected for the absence of the Mtv-2 locus with the early maammary tumour (EMT) test and during the later cycles with the immunodiffusion (ID) test for MTV-antigens in the milk. After six cycles of cross-intercross, brother-sister mating was started with mice selected for the absence of Mtv-2. After two brother-sister matings the milk-transmitted MTV was eliminated by foster-nursing. Of the foster-nursed subline 233 mice (16 of the first, 118 of the second and 99 of the third generation) were tested for the presence of Mtv-2 with one or two of the following three methods: (1) ID-test, (2) EMT-test and (3) by examination of the development of spontaneous mammary tumours in breeding females. The tests were negative in 226 mice. This indicates that Mtv-2 was absent in nearly all mice of the congeneic subline. The positive reactions in the seven other tested mice were weaker than that observed in the GR strain and in GR mice foster-nursed by BALB/c. The presence of the Mtv-2 gene in the seven positive mice of the congeneic line is doubtful. With the ID test, viral antigens were detectable in 50% of the milk samples from the first lactation period of mice of the segregating backcross I population [GR congeneic X (GR congeneic X GR)], indicating a one-gene difference between the congeneic GR line and the progenitor GR strain.
基于先前的观察结果，即Mtv-2控制着妊娠依赖性乳腺肿瘤的出现以及乳腺肿瘤病毒（MTV）抗原在乳汁中的早期表达，人们试图通过引入C57BL/10品系的遗传物质来培育一个不含该基因座的同源GR品系。为此采用了回交-互交系统。通过早期乳腺肿瘤（EMT）试验筛选偶数代小鼠中不存在Mtv-2基因座的个体，并在后续世代中通过免疫扩散（ID）试验检测乳汁中的MTV抗原。经过六个回交-互交周期后，开始对筛选出的不存在Mtv-2基因座的小鼠进行兄妹交配。经过两次兄妹交配后，通过代乳消除乳汁传播的MTV。对代乳的亚系中的233只小鼠（第一代16只、第二代118只和第三代99只）采用以下三种方法中的一种或两种检测Mtv-2的存在：（1）ID试验；（2）EMT试验；（3）检查繁殖雌性小鼠自发性乳腺肿瘤的发生情况。226只小鼠的检测结果为阴性。这表明同源亚系中几乎所有小鼠都不存在Mtv-2。另外七只检测小鼠的阳性反应比GR品系以及由BALB/c代乳的GR小鼠中观察到的反应弱。同源系中七只阳性小鼠中Mtv-2基因的存在情况存疑。通过ID试验，在分离回交I群体[GR同源系×（GR同源系×GR）]小鼠第一个泌乳期的50%乳汁样本中可检测到病毒抗原，这表明同源GR品系与亲本GR品系之间存在一个基因差异。
