The fusion of an AKR T cell tumor line to normal B6D2F1, T cells resulted in the production of a cloned T cell hybridoma (FS6-14.13) inducible with the mitogen concanavalin A (Con A). The supernate from Con A-stimulated hybridoma cells was active both in the stimulation of an anti-sheep red blood cell response by partially T cell-depleted B cells and in the stimulation of the growth of antigen-specific T cell blasts. The active principle in both assays had a molecular weight of approximately 30-40,000. These results indicated the presence of interleukin 2 (IL2) in the hybridoma supernate. The activity of the hybridoma supernate in B cell responses was dependent on the presence of adherent cells and a few contaminating T cells. On the other hand, Con A-stimulated supernates from normal spleen cells were active after either adherent cell removal or severe T cell depletion. These results suggested that IL2 was the only active helper factor in the hybridoma supernate, but that additional helper factors were present in supernates from Con A-stimulated normal spleen cells.

Hybridomas from spleen cell fusions of six BALB/c mice immunized with-hypothalamus were analyzed by immunocytochemistry for antibodies reactive with paraffin sections of fixed rat brain. In a total of 135 antibody producers, 60% were brain specific. Among these, 54% reacted with glial elements, pituitary cells, or basal lamina of intracerebral capillaries, with little variation among individual hybridomas in each of these groups. Forty-six percent ofbrain-specific antibodies reacted with neuronal structures, localizing on nerve fibers, neurofibrils, or perikarya. Neuron-specific hybridomas could be classified into groups that localized in anatomically defineable overall patterns. Within these patterns individual hybridomas exhibited extensive qualitative localization diversity ("neurotypy"). Conceivably, the genetic message for a common "proantigen" within an overall pattern may be slightly modified during differentiation of a neuron, thus leading to minor variability in antigenic expression. During antibody formation, similar minor changes occur in the differentiation of the genetic message for the antibody variable region. Apparently, minor changes in the antibody combining site among groups of hybridomas is reflected in -the detectability of minor neurotypic changes among differentiated neuronal proantigens. If neurotypy proves to be the result of single-base substitutions or of variability in alignment of peptide-coding exons, the Scharrer concept of the fundamental significance of neurosecretion could also become applicable to neuronal specialization.The Scharrer concept of the fundamental biologic role of neurosecretion (1, 2) ushered in the discovery ofan increasing number of neuropeptides in diverse regions of the nervous system (3). The existence of more than one peptide sequence in individual prohormones (4-7) and the coexistence in a single cell of given peptides with a variety of other peptides, unsuspected from the structure of known prohormones (8-11), suggest a great variability in the expression of prohormones among different neurons. On the supposition that such differences may be an expression of the functional diversity of "experienced" neurons, we explored its existence with the use of hybridoma antibodies to whole brain homogenate. Because each monoclonal antibody is reactive with a single antigenic determinant, it defines an antigen even ifit has not been chemically isolated. The only requirement for such application of monoclonal antibodies was the use of a technique for their detection that does not require availability of isolated antigen. Immunocytochemical analysis fulfills this requirement, because it defines an antibody clone by the anatomical distribution of its localization rather than the nature of the antigen with which it reacts. With the use of immunocytochemistry for intracellular antigens, we have found that a large proportion of antibodies to whole brain are brain specific, and that among these a sizeable fraction is neuron specific. MATERIALS AND METHODSSix BALB/c m...

Purified calf thymus DNA polymerases delta I and II each have an associated 3' to 5' exonuclease but otherwise resemble DNA polymerase alpha in size, biochemical kinetic parameters, and the presence of DNA primase [Crute, J. J., Wahl, A. F., & Bambara, R. A. (1986) Biochemistry 25, 26-36]. Here we demonstrate a functional association of polymerase and exonuclease with each delta form. Furthermore, we show that the exonuclease can be dissociated from DNA polymerase delta I but does not appear to be removable from DNA polymerase delta II. Polymerases delta I, delta II, and alpha are equally sensitive to the inhibitor aphidicolin, suggesting a similarity in active site structure. In comparison with DNA polymerase alpha and delta II, DNA polymerase delta I has intermediate sensitivity to 2-(p-n-butylanilino)-2'-deoxyadenosine 5'-triphosphate (BuAdATP) or N2-(p-n-butylphenyl)-2'-deoxyguanosine 5'-triphosphate (BuPdGTP). The activity of the DNA primase of the delta II enzyme is insensitive to BuAdATP whereas 1.0 microM of this inhibitor will decrease the activity of the DNA primase of the alpha and delta I enzymes approximately 50%. Two monoclonal antibodies that potently inhibit DNA polymerase alpha are only slightly inhibitory to DNA polymerase delta I and are ineffective at inhibiting DNA polymerase delta II. DNA polymerase delta II had been previously found to be nearly inactive on nuclease-treated calf thymus DNA, relative to its activity on homopolymeric DNA. We find that addition of purified calf histone proteins or spermidine can greatly enhance synthesis by this enzyme on activated calf DNA.

A rapid, three-step purification of DNA alpha-polymerase from calf thymus is described. The key feature is immunoaffinity chromatography using a column of immobilized monoclonal immunoglobulin G (IgG) developed against human KB cell alpha-polymerase. This step is followed by preparative sucrose gradient sedimentation. The highly purified polymerase has a specific activity of 35 000 nmol of nucleotide incorporated per hour per milligram. Its molecular weight is 404 000. This molecular weight is higher than observed in some earlier purifications, possibly because salt concentrations are kept at nearly physiological levels. Also, the rapidity of purification in the presence of multiple protease inhibitors minimizes degradation. The purified enzyme is inhibited by aphidicolin, N-ethylmaleimide, and the specific monoclonal IgG, thereby identifying it as DNA alpha-polymerase. ATP at 4 mM concentration stimulates enzymatic activity up to 4-fold on calf thymus DNA templates. The enzyme is also capable of priming single-stranded DNA with RNA. The procedure represents a significant advance from purifying alpha-polymerase from calf by conventional means, since it avoids ion-exchange chromatography and harsh conditions. It also minimizes the time required to produce sufficient quantities of purified high molecular weight polymerase for analysis.

Cultured cells of the murine lung carcinoma called line 1 express very low levels of H-2 class I antigens and are resistant to lysis mediated by alloreactive T cells. In order to investigate how the expression of class I antigens affects the in vivo growth of this spontaneous tumor, H-2DP genes were transferred into line 1 cells. Cloned transfectants that displayed H-2DP surface antigens were identified using flow cytometry. The transfected H-2DP antigens appeared normal by twodimensional gel electrophoresis and could also function as excellent targets for T-cell-mediated lysis in vitro. Marked differences in tumorigenicity (defined as tumor growth in immunologically competent hosts) were observed between the DP transfected cells and untransfected or control transfected line 1 cells in syngeneic mice only if the animals had previously received injections of irradiated DP transfectants. Expression of DP antigens did not appreciably affect the growth of line 1 tumors in immunologically naive syngeneic mice or necessarily cause rejection in allogeneic mice. Our in vivo results show that increased expression of class I antigens can reduce the growth of tumors like line 1 that lack all class I antigens. Our results also suggest that increasing class I antigens alone on some spontaneous tumors deficient in expression will not by itself be sufficient for tumor rejection.