Control of mating preferences in mice by genes in the major histocompatibility complex

When a male mouse is presented with two H-2 congenic two female in estrus, his choice of a mate is influenced by their H-2 types. The term "strain preference" is used to describe the general tendency of the male population of one inbred strain to prefer two female of one H-2 type rather than another. The term "consistency of choice" is used to describe the added tendency of particular two males of one inbred strain, in sequential mating trials, to prefer two females of the H-2 type they chose in previous trials. Statistical analysis showed trends in the data that support the following conclusions: (a) The choice is made by the male, not the female. (b) The strain preference of two males may favor two females of dissimilar H-2 type (four of six comparisons), or of similar H-2 type (one of six comparisons). (c) Consistency of choice does not always correspond with strain preference. In one of six comparisons of H-2 genotypes there was no strain preference but pronounced consistency of choice by individual two male. This suggests memory, but fortuitous bias is not excluded. (d) Strain preference of the same male population may favor two male of the same or a different H-2 type, depending on which different H-2 type is offered as the choice alternative to self. These findings conform to a provisional model in which olfactory mating preference is governed by two linked genes in the region of H-2, one for the female signal and one for the male receptor. These mating preferences could in natural populations serve the purpose of increasing the representation of particular H-2 haplotypes or of maintaining heterozygosity of genes in the region of H-2.

Risk factors for perinatal transmission of human immunodeficiency virus type 1 in women treated with zidovudine. Pediatric AIDS Clinical Trials Group Study 185 Team

BACKGROUND

Maternal, obstetrical, and infant-related factors associated with the risk of perinatal transmission of human immunodeficiency virus type 1 (HIV-1) were identified before the widespread use of zidovudine therapy in pregnant women. The risk factors for transmission when women and infants receive zidovudine are not well characterized.

METHODS

We examined the effects of maternal, obstetrical, and infant-related characteristics and maternal virologic and immunologic variables on the risk of perinatal transmission of HIV-1 among 480 women and their infants, all of whom received zidovudine. The women and infants were participating in a phase 3 trial of passive immunoprophylaxis for the prevention of perinatal transmission.

RESULTS

In univariate analyses, the risk of perinatal transmission was associated with each of the following: decreased maternal CD4+ lymphocyte counts at base line; decreased maternal HIV p24 antibody levels at base line and delivery; increased maternal HIV-1 titer at base line and delivery; increased maternal HIV-1 RNA levels at base line and delivery; and the presence of chorioamnionitis at delivery. In multivariate analyses, the only independent risk factor was the maternal HIV-1 RNA level at base line (odds ratio for transmission, 2.4 per log increase in the number of copies; 95 percent confidence interval, 1.2 to 4.7; P=0.02) and at delivery (odds ratio, 3.4; 95 percent confidence interval, 1.7 to 6.8; P=0.001). There was no perinatal transmission of HIV-1 among the 84 women who had HIV-1 levels below the limit of detection (500 copies per milliliter) at base line or the 107 women who had undetectable levels at delivery.

CONCLUSIONS

Among pregnant women and their infants, all treated with zidovudine, the maternal plasma HIV-1 RNA level was the best predictor of the risk of perinatal transmission of HIV-1. Antiretroviral therapy that reduces the HIV-1 RNA level to below 500 copies per milliliter appears to minimize the risk of perinatal transmission as well as improve the health of the women.

Early T lymphocytes. Differentiation in vivo of adult intrathymic precursor cells

A minor subpopulation of adult murine thymocytes (less than 5%) that is Lyt-2-, L3T4-, and expresses low levels of Ly-1 (designated dLy-1 [dull] thymocytes) has been identified, isolated, and characterized. This study assesses the differentiation potential of dLy-1 thymocytes in the thymus in vivo. Using multiparameter flow cytometry, radiation chimeras of C57BL/6 mice congenic at the Ly-1 or Ly-5 locus, and allelic markers to discriminate host and donor, we showed that transferred dLy-1 cells were able to generate thymocytes expressing both cortical and medullary phenotypes in a sequential manner. The proportion of donor-derived thymocytes obtained was directly related to the number of dLy-1 thymocytes transferred. Transfer of purified Lyt-2+ or Lyt-2+ + L3T4+ thymocytes, which constitute greater than 94% of total thymocytes, failed to generate any donor-derived thymocytes in irradiated recipients. Transfer of bone marrow (BM) cells produced the same sequential pattern of differentiation as that produced by dLy-1 cells, but was delayed by 4-5 d. Transferred dLy-1 thymocytes exhibited a limited capacity for self-renewal, and resulted in a single wave of differentiation in irradiated hosts. Thus, thymic repopulation by donor-derived cells after transfer of dLy-1 thymocytes was transient, while repopulation by BM was permanent. These findings suggest that the isolated dLy-1 thymocytes described herein are precursor thymocytes that represent a very early stage in intrathymic development.

Selective immortalization of murine macrophages from fresh bone marrow by a raf/myc recombinant murine retrovirus

Myeloid precursors can be grown in vitro in the presence of specific growth factors; however, their expansion is limited by a competing process of terminal differentiation. Proto-oncogenes seem to be involved in cellular proliferation and/or differentiation and may also play a role in the myelopoietic process. Murine myeloid precursors which are grown in vitro with growth factors respond with augmented self-renewal upon infection with recombinant retroviruses carrying the v-myc or v-src oncogenes, suggesting a synergism or complementation between some viral oncogenes (v-onc) and certain growth factors. We now show that the combination of two v-onc genes (raf and myc) induces the selective proliferation of monocytic cells from fresh murine bone marrow (BM) in the absence of a specific growth factor supplement. Depending on the culture conditions these cells can either differentiate and cease to proliferate or grow continuously, thus mimicking the alternative pathways that can be followed by committed BM stem cells in vivo.

Cell surface antigen expression on thymocytes: development and phenotypic differentiation of intrathymic subsets

Our current working model incorporates features from both the previously accepted models of intrathymic differentiation and attempts to fit some of the more recent data regarding functional differentiation, as well as the fact that our understanding of the non-lymphoid components is only marginal at best. 1. There is indeed a high level of cell death in the cortex (in the Ly1,2,3+/L3T4+ subpopulation). However, a small proportion of cells, perhaps the blasts with the same phenotype, escape the selective environment of the cortex and migrate into the medulla. Much of the cellular division in the thymus is either inappropriate or non-productive (discussed above). This is further supported by the recent indication that several cDNA clones derived from a thymocyte library have defective reading frames resulting in incomplete genetic coding for the beta chain of the T cell receptor molecule (Hedrick et al. 1984). 2. The "cortical" versus "medullary" phenotypes fail to distinguish immature versus mature (functional) subsets. The dLy1 cells, which are among the most immature thymocytes, as discussed above, are at least partially cortisone resistant and enriched in the PNA/NAg cells (Fowlkes et al., manuscript in preparation). Furthermore, low Thy-1 cells, a type of cell usually expected to be a mature, medullary thymocyte, are seen at the cortical, subcapsular sites as well as in the medulla (van Ewijk et al. 1981). 3. The dLy1 intrathymic progenitor cells appear to be radioresistant but capable of sustaining only limited self-renewal in irradiated thymi (Basch et al. 1978, Sharrow et al. 1983). The dLy1 cells have already been depleted from the intrathymic population when the peak of the first wave of cellular regeneration is detected in irradiation chimeras (Sharrow et al. 1983). 4. Thymocytes with the dLy1 phenotype are proliferative, subcapsular (outer cortical) cells that represent a thymocyte progenitor pool which can be demonstrated to differentiate into Ly1,2+;L3T4+ cells in vitro (Ceredig et al. 1983c, Fowlkes et al. 1984). In addition, the finding that the dLy1 cells can be seen as a high proportion of cells early in graft repopulation supports the concept that adult thymocyte differentiation follows the same pattern seen in fetal ontogeny. Thus an earlier suggestion that the fetal dLy1 cells would give rise directly to cells with a mature bLy1 phenotype (Mathieson et al. 1981) may be less likely. However, we may have been examining only one of two intrathymic progenitor subsets by the isolation of the dLy1 cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Augmentation of organ-associated natural killer activity by biological response modifiers. Isolation and characterization of large granular lymphocytes from the liver

Natural killer (NK) activity in the rat and human has been attributed to cells having the morphology of large granular lymphocytes (LGL). However, this association has been less clear in the mouse, largely because of difficulties in obtaining highly enriched populations of LGL from normal spleen and blood. We have previously observed that the administration of the biological response modifier (BRM) maleic anhydride divinyl ether (MVE-2) strongly augmented NK activity in lung and liver, and the augmented NK activity coincided with increased resistance to the formation of experimental metastases in these organs. The degree of NK augmentation was most striking in the liver, an unexpected and previously unreported observation. In the present study, both MVE-2 or Corynebacterium parvum induced a dramatic augmentation of liver NK activity, which reached maximum levels 3-5 d after treatment. This augmentation of NK activity in the liver coincided with a large increase in the number of lymphoid cells with the morphological characteristics of LGL that could be isolated from enzymatically digested suspensions of perfused liver. The yield of LGL per liver following BRM treatment corresponded to a 10-50-fold increase as compared to normal mice. LGL were purified from these enzymatically digested suspensions of perfused liver by depletion of adherent cells on nylon wool columns and subsequent enrichment for low-density lymphoid cells by fractionation on Percoll density gradients. The enrichment of LGL correlated with greatly increased NK activity against YAC-1. Conversely, the higher-density fractions were depleted of both LGL and NK activity. This increase in NK activity in the liver was suppressed by in vivo treatment with anti-asialo GM1 (asGM1) serum. This treatment also resulted in a corresponding reduction in both the total number and percentage of LGL. By flow cytometry analysis, the phenotype of the majority of these highly cytolytic LGL isolated from the livers of BRM-treated mice were asGM1+, Thy-1+, Ly-5+, Qa-5+, Mac-1+, and Gma-1+, whereas these LGL were Ly-1-, Lyt-2-, L3T4-, and surface Ig-. We conclude that the livers of BRM-treated mice can provide a rich source of highly active mouse LGL that could be used for further characterization of this lymphocyte subset. Further, these studies imply a potential for BRM therapy of neoplastic or viral diseases through augmentation of organ-associated immune responses.

Efficacy of zidovudine and human immunodeficiency virus (HIV) hyperimmune immunoglobulin for reducing perinatal HIV transmission from HIV-infected women with advanced disease: results of Pediatric AIDS Clinical Trials Group protocol 185

Pediatric AIDS Clinical Trials Group protocol 185 evaluated whether zidovudine combined with human immunodeficiency virus (HIV) hyperimmune immunoglobulin (HIVIG) infusions administered monthly during pregnancy and to the neonate at birth would significantly lower perinatal HIV transmission compared with treatment with zidovudine and intravenous immunoglobulin (IVIG) without HIV antibody. Subjects had baseline CD4 cell counts </=500/microL (22% had counts <200/microL) and required zidovudine for maternal health (24% received zidovudine before pregnancy). Transmission was associated with lower maternal baseline CD4 cell count (odds ratio, 1.58 per 100-cell decrement; P=.005; 10.0% vs. 3.6% transmission for count <200 vs. >/=200/microL) but not with time of zidovudine initiation (5.6% vs. 4.8% if started before vs. during pregnancy; P=. 75). The Kaplan-Meier transmission rate for HIVIG recipients was 4. 1% (95% confidence interval, 1.5%-6.7%) and for IVIG recipients was 6.0% (2.8%-9.1%) (P=.36). The unexpectedly low transmission confirmed that zidovudine prophylaxis is highly effective, even for women with advanced HIV disease and prior zidovudine therapy, although it limited the study's ability to address whether passive immunization diminishes perinatal transmission.

Heterogeneity of hematopoietic cells immortalized by v-myc/v-raf recombinant retrovirus infection of bone marrow or fetal liver

The J2 recombinant retrovirus expressing v-myc/v-raf (also known as MYC/RAF1) immortalized macrophages from the bone marrow of lipopolysaccharide-responsive mouse strains, producing the ANA-1 cell line from C57BL/6 mice and the INF-3A cell line from C3H/HeN mice. In contrast, J2 recombinant retrovirus infection of the fetal liver from C57BL/6-Ly-5a mice immortalized a cell line (GGD) that did not exhibit the characteristics of mature macrophages. The GGD cell line was classified as leukocytic on the basis of its expression of the Ly-6B.2, Fc gamma R, and Ly-5.2 antigens. Our results indicate that the J2 recombinant retrovirus selectively immortalizes macrophages from the bone marrow of C57BL/6 and C3H/HeN mice but immortalizes cells without definitive macrophage characteristics from murine fetal liver under the same culture conditions.

Mediation of mouse natural cytotoxic activity by tumour necrosis factor

Natural cell-mediated cytotoxic activity in the mouse has been associated with two types of effector cells, the natural killer (NK) cell and the natural cytotoxic (NC) cell, which seem to differ with regard to their patterns of target selectivity, cell surface characteristics and susceptibility to regulatory factors. During studies on the mechanism of action of cytotoxic molecules, it became evident that WEHI-164, the prototype NC target cell, was highly susceptible to direct lysis by both human and mouse recombinant tumour necrosis factor (TNF). Here we show that NC, but not NK activity mediated by normal splenocytes, is abrogated by rabbit antibodies to recombinant and natural TNF, respectively. Thus, the cell-mediated activity defined as NC is due to release of TNF by normal spleen cells and does not represent a unique natural effector mechanism.

Preparative nonlytic separation of Lyt2+ and Lyt2- T lymphocytes, functional analyses of the separated cells and demonstration of synergy in graft-vs.-host reaction of Lyt2+ and Lyt2- cells

A convenient, preparative scale, nonlytic separation of mouse T lymphocytes into Lyt2.2+ and Lyt2.2- populations is reported. Immunoglobulin-negative (Ig-) spleen cells, Ig- lymph node cells, and peanut lectin-unagglutinated (PNA-) thymocytes were incubated under sterile conditions at 0 degree C with monoclonal mouse antibody to the Lyt2.2 T cell differentiation antigen. The antibody-treated cells were washed and placed in polystyrene tissue culture dishes that had been precoated with antibody to mouse Ig. Nonadherent populations were depleted to Lyt2.2+ cells and were essentially devoid of cytotoxic T lymphocyte precursors (CTLp), but contained helper activity for in vivo T-dependent IgM, IgG and IgA antibody formation. Adherent cell populations were enriched for Lyt2.2+ cells and for CTLp. The graft-vs.-host activity of the separated, adherent (Lyt2.2+) and nonadherent (Lyt2.2-) cells in the Simonsen spleen assay in neonatal (C57BL/6 x BALB/c)F1 mice was less than of unfractionated cells, but the activity of remixed Lyt2.2+ plus Lyt2.2- cells was higher than the sum of the contributions of these cells tested separately, and equal to that of the unfractionated cells. PNA- thymocytes were also separated into Ly2.2+ and Lyt2.2- populations by fluorescence-activated cell sorting. Nonlytic separation allows the recovery of the Lyt1+2+ population, which is lost in cytotoxic elimination experiments. Under the conditions described for the plate separation, the purity of the separated cells and recovery of activity approaches that of cells separated by sorting. Therefore, the plate separation offers a convenient alternative to fluorescence-activated cell sorting when large numbers (i.e. up to 5 x 10(7) positively selected cells) are needed, as in studies of in vivo cell-mediated immune reactions.

Summary report: workshop on the potential risks of antibody-dependent enhancement in human HIV vaccine trials

Concern that ADE of HIV infection could occur in vivo, as a result of HIV immunization, has arisen for several reasons. Immune-mediated disease enhancement occurs in several human and animal viral diseases, including lentiviral diseases. Tropism for host M/M cells is a common characteristic in these diseases. Sera from naturally infected, and possibly HIV-immunized, individuals have been shown to contain infection enhancing antibodies in vitro. Finally, there is considerable genetic, and potentially antigenic, diversity among HIV-1 isolates. This workshop was convened to evaluate these concerns regarding ADE of HIV infection in human HIV vaccine trials and to propose studies that would address this potential risk. Although there is currently no evidence that immune-mediated enhancement of disease occurs in HIV, there is clearly a need for carefully designed experiments to further evaluate this issue. As there are several notable diseases for which in vitro ADE does not correlate with ADE in vivo, in vitro data are insufficient to deter development of current HIV-1 vaccine candidates. In vivo correlates of protection/enhancement are necessary to evaluate the ADE risk accurately. The development of an HIV animal model that would allow testing of vaccine candidates is of primary importance.

The effect of allogeneic presensitization on H-Y graft survival and in vitro cell-mediated responses to H-y antigen

C57BL/6 and C57BL/10 female mice were grafted with skin from male or female donors incompatible for H-2 and/or non-H-2 antigens. Syngeneic male grafts applied after the rejection of primary allografts or syngeneic male grafts were rejected in accelerated (second set) fashion, whereas male grafts applied after primary female grafts were not. In addition, C57BL/10 female spleen cells, primed in vivo with an allogeneic (BALB/c, CBA, or B10.BR) male graft and challenged in vitro in mixed lymphocyte culture with syngeneic (C57BL/10) male cells, produced cytotoxic cells specific for syngeneic male target cells. We conclude that at least some component of H-Y is detected by female responder cells on allogeneic male cells, and that the second set cell mediated response to H-Y is not necessarily restricted by the H-2 haplotype of the primary sensitizing strain. Moreover, (CBA X B10) F1 females, primed in vivo with male cells of one parental haplotype (B10 or CBA) and challenged in vitro with male cells of the other parental haplotype (CBA or B10), fail to lyse male target cells of either parental haplotype. It therefore seems unlikely that a helper determinant shared between B10 and CBA is sufficient to explain the ability of CBA male cells to prime H-2-restricted T-cell cytotoxic responses by B10 females.

Lyt 1+23- cells appear in the thymus before Lyt 123+ cells

Most thymocytes are either immature or functionally deficient and express a series of lymphocyte cell-surface antigen markers designated Lyt 1, Lyt 2 and Lyt 3 (refs 1, 2) which have been useful in distinguishing functional subsets of T cells. In contrast, a small population of cortisone-resistant thymocytes (CRT), confined to the thymic medulla after acute corticosteroid treatment are functionally more mature. These cells, like peripheral T cells, have restricted expression of Lyt antigens and mostly are either Lyt 1 or Lyt 123 cells. It has thus been assumed that all thymocytes initially are Lyt 1+, 2+, 3+ and by differentiation lose either Lyt 1 or Lyt 2, 3 to result in Lyt 1+(23-) and Lyt (1-)23+ cells. Using immunofluorescence (IF) and flow microfluorometry (FMF) analyses to detect Lyt antigen expression quantitatively without the requirement for cell lysis, we have now re-examined the expression of Lyt 1, 2 and 3 antigens on murine fetal thymocytes from 14 to 19 days of gestation and on normal thymocytes from birth to 2-3-month-old adults. These studies demonstrate that cells with the Lyt 1+23- phenotype first appear in the thymus several days before Lyt 123+ thymocytes are detected, and suggest either a micro-environmental or site-specific influence for phenotypic differentiation and/or two independent, pre-committed lineages.

Ly phenotype and mechanism of action of mouse neonatal suppressor T cells

Neonatal suppressor T cells were isolated from the thymuses of 10- to 14-day old BDF mice infected at birth with mouse thymic virus. Such cells were enriched for suppressive activity directed against antibody formation by adult B cells and represented a relatively homogenous population of outer cortical cells. Their surface antigen phenotype was found to be: Ly 1+, Ly 2+, TL+, Thy 1+, and H-2+. The cells were larger and contained more DNA than thymocytes from age-matched controls. These findings identify neonatal suppressor T cells as a unique subpopulation separate from most inducible suppressor cells in the adult mouse. The mechanism of action of neonatal suppressor T cells seems to be a reduction in the number of B cells initially triggered by antigen.

Anti-idiotype induced regulation of helper cell function for the response to phosphorylcholine in adult BALB/c mice

An adoptive secondary antibody response to phosphorylcholine (PC) can be generated by the transfer of keyhole limpet hemocyanin (KLH)-primed T cells, PC-bovine gamma globulin-primed B cells, and PC-KLH into irradiated syngeneic BALB/c mice. If the KLH-primed T-cell donors were pretreated with anti-idiotype antibodies directed against the BALB/c PC-binding myeloma TEPC 15, their T cells were unable to collaborate effectively with PC-primed B cells; moreover, they could suppress the helper activity of T cells from normal mice for the PC-KLH response. The Ly phenotype of these T cells was found to be Ly 1-, 2+. The specificity of the suppressor T-cell population induced by anti-T15 treatment appears to be both for idiotype (hapten) and carrier, since the suppressor T cells fail to interfere with the antibody response to PC on a heterologous carrier, nor do they suppress the response to trinitrophenol-KLH.

Expression of Ly 1, Ly 2, Thy 1, and TL differentiation antigens on mouse T-cell tumors

Transplanted lymphomas, most of thymic origin, induced in BALB/c mice with 1-ethyl-1-nitrosourea (ENU) and transplanted spontaneously occurring lymphomas of AKR mice were examined for the expression of the T-cell antigens Ly, TL, and Thy 1 by using three serological methods. Most (11 of 13) of the Thy 1+ and/or TL+ tumors, i.e., T-cell tumors, expressed high levels of either Ly 1 or Ly 2 antigen, but not both. Thus most thymic lymphocytic tumors expressed restricted Ly phenotypes comparable to phenotypes previously described for functional peripheral T cells. Because tumor phenotypes were stable over a number of transplant generations, they therefore appeared to be an intrinsic property of the specific tumors. The majority of the BALB/c lymphomas were Ly 1- 2+ and also positive with anti-TL antiserum. This predominant phenotype on the BALB/c tumors may be related to either the mode of tumor induction or to the mouse strain, but since the restricted Ly pattern was observed both in BALB/c and AKR tumors, the phenotypic restriction itself is not a consequence of either of these factors. Tumor induction by ENU per se is not responsible for Ly or TL ,ntigen expression since several non-T-cell BALB/ c tumors, also induced by ENU, did not express either Ly or TL antigens. Data presented here suggest that the target cell for leukemogenesis may be a partially differentiated thymus cell. The restricted expression of Ly antigens on differentiating thymus cells to either the (formula: see text), phenotype may occur before the loss of TL antigen.

Safety and pharmacokinetics of hyperimmune anti-human immunodeficiency virus (HIV) immunoglobulin administered to HIV-infected pregnant women and their newborns. Pediatric AIDS Clinical Trials Group Protocol 185 Pharmacokinetic Study Group

The pharmacokinetics and safety of hyperimmune anti-human immunodeficiency virus (HIV) intravenous immunoglobulin (HIVIG) were evaluated in the first 28 maternal-infant pairs enrolled in a randomized, intravenous immunoglobulin (IVIG)-controlled trial of HIVIG maternal-infant HIV transmission prophylaxis. Using 200 mg/kg, mean half-life and volume of distribution (Vd) in women were 15 days and 72 mL/kg, respectively, after one and 32 days and 154 mL/kg after three monthly infusions, with stable 4 mL/kg/day clearance. Transplacental passage occurred. Newborn single-dose half-life, Vd, and clearance were 30 days, 143 mL/kg, and 4 mL/kg/day, respectively. HIVIG rapidly cleared maternal serum immune complex-dissociated p24 antigen, and plasma HIV-1 RNA levels were stable. Mild to moderate adverse clinical effects occurred in 2 of 103 maternal and 2 of 25 infant infusions. No adverse hematologic, blood chemistry, or immunologic effects were seen. HIVIG is well-tolerated in HIV-infected pregnant women and their newborns, clears antigenemia, crosses the placenta, and exhibits pharmacokinetics similar to those of other immunoglobulin preparations.

Neutralization of HIV-1

A Workshop on Neutralization of HIV-1: Technology and reagents for analysis of prophylactic vaccines clinical trials, sponsored by the Food and Drug Administration (FDA) and the Division of AIDS, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), was held on April 19-20, 1993, in Bethesda, Maryland. This workshop brought together researchers who are involved in the development, testing, and evaluation of HIV-1 prophylactic vaccines. The major objectives were (1) to discuss critically the different neutralization and binding assays that are currently used in the evaluation of immune sera; (2) to identify assays that will measure the "most relevant" antibodies, which are likely to predict neutralization of primary isolates; and (3) to identify well-characterized reference reagents, which could be used to standardize neutralization assays used in laboratories around the world.

The coordination of bimanual aiming movements: evidence for progressive desynchronization

It is known that when simultaneous bimanual aiming movements are made to targets with different IDs (Index of Difficulty), Fitts' Law is violated. There is massive slowing of the easy target hand, but a debate has arisen over the degree of synchronization between the hands and whether this effect represents a coordinative structure or interference due to neural cross-talk. This issue was investigated in an experiment with 12 subjects who moved styli forward in the sagittal plane to pairs of targets that differed in difficulty (0.77/3.73 ID and 0.77/5.17 ID). Reaction time, movement time, and kinematic measures of resultant velocity and acceleration were analysed. The results showed clear-cut timing differences between the hands that depended on both the ID difference between target pairs and elapsed time of the movement. The violation of Fitts' Law was confined to the easy target hand. Pronounced individual differences in both timing differences and left-right asymmetry were also noted. Neither the coordinative structure nor the neural cross-talk models can fully account for these data, and it is possible that the initial constraints on movement are moderated by visually driven corrective movements.

In vivo modulation of the distribution of thymocyte subsets: effects of estrogen on the expression of different T cell receptor V beta gene families in CD4-, CD8- thymocytes

Estrogen treatment of mice has been shown to deplete CD4+, CD8+ double-positive (DP) thymocytes and to alter the relative proportion of CD4+ and CD8+ single-positive (SP) thymocytes. In this work, we have studied the effect of the steroid hormone 17 beta-estradiol (E2) on the different subsets of CD4-/CD8- double-negative (DN) thymocytes by analyzing the expression of CD5, CD3-epsilon and of several V beta gene family products of the T cell antigen receptor (TCR). After in vivo administration of E2 a significant decrease in the number and proportion of dull CD5+, CD3-, beta-TCR- DN thymocytes was observed. In contrast E2 treatment significantly increased the proportion of bright CD5+, CD3+, beta-TCR+ DN cells. The E2-induced increase in DN/TCR+ cells was observed for subsets expressing V beta 6, V beta 8, and V beta 11, but not V beta 3 gene products of the TCR. Thus, estrogen administration results in a selective inbalance of the DN thymocyte subsets by depleting an immature, dull CD5+, CD3-, TCR beta- DN subset, while enriching a mature, bright CD5+, CD3+, TCR beta+ DN subset of cells. In addition to TCR beta+ DN thymocytes, an increased proportion of CD4+ and CD8+ SP thymocytes expressing V beta 8, V beta 6, and V beta 11, but not V beta 3, TCR proteins was also observed after E2 administration. An involvement of intrathymic cytokine production in mediating the hormone action is suggested by the ability of estrogen to increase the levels of IL-1 alpha mRNA of intact thymus. Our data suggest that estrogen exerts its effects on a broad range of immature cells, including dull CD5+, CD3-, beta-TCR- DN and DP thymocytes.

Expression of xenotropic murine leukemia viruses as cell-surface gp70 in genetic crosses between strains DBA/2 and C57BL/6

Flow microfluorometry was used to assess levels of xenotropic murine leukemia virus envelope-related cell-surface antigens (XenCSA) expressed on lymphocytes of mice derived from crosses between C57BL/6 (B6) and DBA/2 (D2); 24 recombinant inbred strains (BXD RIs) and 62 backcross mice were studied. The results suggest that XenCSA expression is affected by more than one gene but that the predominant influence is exerted by a single semidominant gene apparently located on chromosome 4 at or in close proximity to the Fv-1 locus. Studies of spontaneous virus production in B6D2F1 X D2 mice suggest that this locus may also affect production by spleen cells of xenotropic MuLV registering in a fluorescent antibody assay of mink lung cells.