Antigen-binding cells in human fetal liver

Experimental autoimmune encephalomyelitis in mice: antigen binding lymphocytes to basic protein of myelin in susceptible and resistant strains

Antigen-binding lymphocytes (ABL) to basic protein of myelin (BPM) were demonstrable in the thymus and spleen of various strains of mice. Counts of ABL did not differ in strains resistant and susceptible to EAE, and did not differ when human or murine 125I-labelled BPM was used as a labelled antigen to detect ABL. After injection with mouse spinal cord and adjuvants, under conditions known to be immunogenic and encephalitogenic for susceptible strains of mice, counts of ABL increased two- to four-fold in suceptible strains but did not icnrease in resistant strains. Antigen binding could not be accounted for by the attachment to cells of cytophilic antibody with specificity for BPM, because such antibody was seldom demonstrable even after immunization. Inferences from the study were: (i) that tolerate (non-responsiveness) to certain autoantigens at least must depend on control over continually present antigen-reactive lymphocytes rather than on any lack of capacity to recognize antigen; (ii) differences in susceptible and resistant strains are evident after, rather than before, immunization.

Ontogeny of lymphocyte subpopulations in human fetal liver

Lymphocytes were isolated from five fetal livers (13-17 weeks) and examined for different surface markers. Immunoglobulin M was found on 0.5-4.0% of lymphocytes. No membrane-bound surface IgD, IgA. or IgG was detected. Mouse erythrocyte rosette-forming lymphocytes ranged from 0.5 to 6.0%. Thymus-processed (T) lymphocytes, which were defined as those forming spontaneous rosettes with sheep erythrocytes, as well as lymphocytes with IgG Fc receptors, were present in a small proportion. No complement-receptor-bearing lymphocytes were found in the two cell populations of fetal liver studied. It is evident that during the ontogeny of bone-marrow-derived (B) lymphocytes IgM is the first surface immunoglobulin to appear. Receptors for the binding of mouse erythrocytes are present at the same time as surface IgM. The slight excess of mouse erythrocyte rosette-forming cells over cells having surface immunoglobulin M could mean that IgM appears later than do the receptors for the binding of mouse erythrocytes.