Joyce A. Filppi

Antigenic cross-reactivity among rodent brain tissues and stem cells.

SUMMARY Previous studies have shown that antisera prepared in rabbits against mouse brain (RAMB) contains activity in vitro against the mouse bone marrow colony-forming unit (CFU) or hematopoietic stem cell. In the present study, in vitro treatment of mouse bone marrow with antisera prepared in rabbits against brain tissue from rats (BARB) or hamsters (RAHB) also reduced the CFU content of the mouse marrow. Prior absorption of the RAMB serum with fetal liver tissues from rats or hamsters as well as mice reduced the anti-CFU activity of the RAMB preparation. In addition, absorption of the RAMB preparation with brain tissue from any of the rodents reduced the activity of the antiserum for the mouse stem cell. It appears that the determinants previously shown to be shared by the brain tissue and stem cells of mice are cross-reactive with determinants present on the stem cells and brain tissue of rats and hamsters.

Direct identification of the murine pluripotential stem cell using rabbit anti-mouse brain serum.

SUMMARY Previous studies have shown that antisera prepared in rabbits against mouse brain tissue (RAMBS) contain activity against the murine bone marrow colony-forming unit (CFU-s) or pluripotential hemotopoietic stem cell. In the present study, the F(ab′)2 portion of RAMBS was examined for its potential efficacy in the identification of the mouse CFU-s when used in an indirect immunofluorescence-labeling technique. After separation of mouse bone marrow cells by a discontinuous bovine serum albumin density gradient, fluorescent cells were observed only in those bands which, by the splenic colony-forming assay, demonstrated CFU-s. Furthermore, the quantity of CFU-s demonstrated by the spleen colony-forming assay approximated the number of fluorescent cells observed in the corresponding band. It appears that the F(ab′)2 portion of RAMBS used in an immunofluorescent assay may provide a method for the direct quantitation and identification of the CFU-s content of murine bone marrow.

Studies on in vitro colony formation by mouse bone-marrow cells using different sources of colony-stimulating factor.

SummaryConditioned media of a primary mouse embryo and a mouse cell line were compared as sources of colony-stimulating factor. The incorporation of embryo cell conditioned medium into semisolid cultures of mouse bone-marrow cells induced the formation of a larger number of in vitro colonies than did the addition of equal volumes of LM cell conditioned medium. This finding did not appear to be the result of quantitative differences in the levels of C.S.F. between the sources since concentration of the LM cell conditioned preparation did not enhance effectively the number of colonies produced. Both the colonial morphology and the cellular components of the developing colonies were found to differ in accordance with the C.S.F. source employed for stimulation. Colonies that developed under the influence of embryo cell conditioned medium were typically larger and more disperse than were those produced in cultures stimulated with the LM cell conditioned source. The latter colonies were smaller, more compact and contained fewer cells. Differences also were noted in the relative proportion of granulocytes to mononuclear cells comprising the colonies. Those colonies stimulated with LM cell conditioned medium rapidly underwent a transition from primarily a granulocytic composition to one comprised principally of mononuclear cells. Cultures stimulated with embryo cell conditioned medium contained a greater number of granulocytic colonies which persisted for a protracted period during cultivation. The addition of 2-mercaptoethanol to cultures stimulated with embryo cell conditioned medium increased the number of colonies produced. Such synergy did not occur in cultures stimulated with the LM cell conditioned medium.