Abstract
FBJ osteosarcoma virus (FBJ-MSV) isolated originally from a spontaneously arising osteosarcoma in a CF1 mouse is the only known naturally occurring murine sarcoma virus (MSV). It is unique among strains of MSV in producing primarily sarcomata in mice. The capacity of tumour cells transformed in vivo by this agent to elicit specific transplantation immunity in syngeneic hosts was investigated. A low level of resistance (10(4)-10(5) cells) was consistently induced by implantation of x-irradiated (15,000 rad) tumours or surgical excision of developing subcutaneous grafts. By contrast intraperitoneal inoculation of virus containing cellfree extracts of FBJ-MSV sarcomata was a far less effective immunization procedure. Confirmatory evidence for the antigenicity of these neoplasms was obtained in tests in which preincubation of tumour cells with lymphoid cells from specifically immune donors inhibited in vivo outgrowth of the FBJ-MSV cells in untreated syngeneic recipients. The induction of host resistance to FBJ-MSV cells by immunization with identical and independently-induced FBJ-MSV tumours established that FBJ-MSV cells possess common cell surface antigenic specificities in a manner analogous to those of experimental neoplasms induced by other oncogenic DNA and RNA viruses. Since FBJ-MSV cells release infectious virus it was not possible in this system to establish whether the tumour-rejection antigen was cellular or virion in nature. The antigenic weakness of FBJ-MSV cells in syngeneic hosts is comparable with that of virus-induced murine leukaemias of the Gross (G) or "wild" type subgroup to which category FBJ-MSV also belongs. These features suggest that FBJ-MSV exemplifies naturally occurring sarcomagenic viruses more closely than those of the Friend-Moloney-Rauscher-Graffi (FMRGr) subgroup which in general induce highly antigenic neoplasms.
Highlights
Summary.-FBJ osteosarcoma virus (FBJ-MSV) isolated originally from a spontaneously arising osteosarcoma in a CFI mouse is the only known naturally occurring murine sarcoma virus (MSV)
Three procedures were used for studying This procedure depressed the primary the immunogenicity of FBJ-MSV induced response of both groups to the challenge sarcomata passaged in syngeneic hosts: inoculum, without appreciably affecting the (a) Implantation of irradiated tumour iso- secondary response in previously immunized grafts.-Tumour grafts
The immune response evoked by FBJ-MSV induced sarcomata following repeated implantation of irradiated (15,000 rad) tumour grafts was determined by comparison of tumour incidences in immunized hosts with untreated controls
Summary
Passage A (Gross) virus-induced and many Animals.-The animals used in this study spontaneous leukaemias as well as in were male and female CBAT6T6 and CBA(H). Adult CBA(H) mice Cells were washed once by centrifugation received a series of i.p. injections (0 5 ml) of in serum-free Eagles' MEM and the viable cell-free virus preparations the oncogenicity cells enumerated by trypan blue exclusion. Three procedures were used for studying This procedure depressed the primary the immunogenicity of FBJ-MSV induced response of both groups to the challenge sarcomata passaged in syngeneic hosts: inoculum, without appreciably affecting the (a) Implantation of irradiated tumour iso- secondary response in previously immunized grafts.-Tumour grafts All experi- intraperitoneal immunizations with 2 x 106 mental groups received 4 such immunizations x-irradiated (15,000 rad) FBJ-MSV sarcoma at approximately 10-day intervals; (b) Excis- cells in Eagles' MEM. Recipients were palpated weekly for evidence of tumour development at the site ofinjection
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