Immunodeficiency in RFM/(T6xRFM)F1 mouse chimaeras with lethal host-versus-graft syndrome.

Rather than central tolerance, the perinatal inoculation of related F1 hybrid spleen cells into inbred mice may result in host-versus-graft (HVG) reactions manifested as transient autoimmunity, or as a lethal immunodeficiency syndrome. RFM/(T6xRFM)F1 chimaeras with lethal disease die in 30 days with lymphosplenomegaly, immune complexes and impaired immune responses. The present studies used in vitro proliferation assays to show that the HVG reaction caused hyperplasia sufficient to account for the lymphosplenomegaly, while also causing severe impairment of splenic and nodal cell responses to concanavalin A (Con A) and to bacterial lipopolysaccharide (LPS). By 25 days, HVG mice could not distinguish between self and non-self as judged by mixed lymphocyte reactions (MLR) to RFM, (T6xRFM)F1 and third party A/J cells. There were no indications that host cells reactive to F1 donor cells had undergone clonal deletion, anergy or expansion. Flow cytometry revealed that donor T lymphocytes achieved stable engraftment, mostly in the nodes, despite the HVG reaction. Taken together with previous observations, these studies showed that HVG reactions in young parent F1/chimaeras can result in an immunodeficiency state which is characterized by an early appearing, profound and persistent impairment of both host and donor T and B cell functions. The results suggest that HVG reactions can contribute directly to immune deficits seen after clinical allogeneic bone marrow transplantation.     

Expression of murine leukemia viruses in RFM mice with host versus graft disease after perinatal inoculation of (T6 X RFM)F1 lymphohemopoietic cells

Host versus graft disease is the fatal syndrome of altered immunity that follows the perinatal inoculation of related F1 hybrid spleen cells to susceptible strains of inbred mice. The allogenic reaction results in severe depletion of T-lymphocytes, but causes hyperplasia and hypersecretion of B-cells. Among the long-term survivors of acute host versus graft reactions, there is a high incidence of nonthymic lymphomas associated with ecotropic murine leukemia virus that may be of donor F1 origin. The present studies were done to determine whether ecotropic murine leukemia virus played any role in the pathogenesis of acute host versus graft disease in RFM mice perinatally inoculated with (T6 X RFM)F1 spleen cells. In RFM/(T6 X RFM)F1 chimeras, N-tropic murine leukemia virus can be detected as early as 3 days. The progression of the disease was accompanied by increasing viral expression. The inoculation of N-tropic virus of F1 donor origin into RFM neonates failed to induce disease, although the virus proliferated. Detection of progressively rising titers of antibody to murine leukemia virus linked the virus to the development of hyperimmunoglobulinemia by virtue of its ability to serve as a replicating source of antigens. These and other studies provided evidence that the seemingly paradoxical appearance of hyperimmunoglobulinemia in T-cell-deficient mice with the host versus graft syndrome is due, at least in part, to the stimulation of presensitized F1 donor B-cells, which are not destroyed in the allogenic reaction, as are the T-cells. Another unusual finding was the detection of polytropic murine leukemia virus in 25-day-old RFM/(T6 X RFM)F1 chimeras. It is suggested that the allogenic host versus graft reaction favored the formation of recombinants.     

Rat natural killer (NK) cells are not bone marrow dependent

Rats were treated with various doses of 89Strontium. At a dose effecting depletion of the bone marrow (200 muCi), NK activity of spleen, peritoneal and peripheral blood lymphocytes was unaltered or only slightly decreased. At higher doses (400 muCi), a general impairment of the immune system, including T-cell functions, was observed. After application of 700 muCi 89Strontium, rats died within three weeks.     

The role of natural killer (NK) and NK T cells in the loss of tolerance in murine primary biliary cirrhosis

One of the major obstacles in dissecting the mechanism of pathology in human primary biliary cirrhosis (PBC) has been the absence of animal models. Our laboratory has focused on a model in which mice, following immunization with a xenobiotic chemical mimic of the immunodominant autoepitope of the E2 component of pyruvate dehydrogenase complex (PDC-E2), develop autoimmune cholangitis. In particular, following immunization with 2-octynoic acid (a synthetic chemical mimic of lipoic acid-lysine located within the inner domain of PDC-E2) coupled to bovine serum albumin (BSA), several strains of mice develop typical anti-mitochondrial autoantibodies and portal inflammation. The role of innate immune effector cells, such as natural killer (NK) cells and that NK T cells, was studied in this model based on the hypothesis that early events during immunization play an important role in the breakdown of tolerance. We report herein that, following in-vivo depletion of NK and NK T cells, there is a marked suppression of anti-mitochondrial autoantibodies and cytokine production from autoreactive T cells. However, there was no change in the clinical pathology of portal inflammation compared to controls. These data support the hypothesis that there are probably multiple steps in the natural history of PBC, including a role of NK and NK T cells in initiating the breakdown of tolerance. However, the data suggest that adaptive autoimmune effector mechanisms are required for the progression of clinical disease.     

Enrichment of murine splenic natural killer (NK) cells by the sequential elimination of non-NK cells

A simple and reliable three-step procedure to enrich for murine endogenous splenic NK cells is described. The method is based on the sequential elimination of non-NK cell subsets by standard and inexpensive techniques executed in a specific order. First, macrophages and other adherent cells are eliminated by incubation on plastic surface. Secondly, the T cells are excluded from the multicellular aggregates formed by agglutination of the remaining cells with wheat germ lectin. Thirdly, after dissociation of the aggregates with N-acetyl-D-glucosamine and osmotic lysis of erythrocytes, NK cells are separated from other nucleated cells by nylon wool filtration. C57BL/6 spleen cells were used to establish the enrichment procedure. Usually their NK cell activity is intermediate but occasionally either low or high NK cell activity was observed in input cell suspensions. The NK cell activity recovery and the degree of enrichment varied inversely with the initial NK cell activity level of the input cell suspension. When initial NK cell activity was intermediate, it was enriched 10-30-fold. Experiments were done to establish if suppressor cells, and nylon wool-adherent, naturally activated NK cells, putatively present in input cells, could have been responsible for the abnormal initial NK cell activity detected in some C57BL/6 spleen cell suspensions and for the variations in the degree of enrichment achieved by the method here described. Either no or negligeable suppressor cell activity was noted in the cell fractions normally discarded at each step of the procedure. On the other hand, nylon wool-adherent NK cells were eliminated during the fractionation of spleen cells with higher than average initial NK cell activity and would account for the lower NK cell enrichment obtained in these conditions.     

Lower numbers of circulating natural killer T (NK T) cells in individuals with human T lymphotropic virus type 1 (HTLV‐1) associated neurological disease

Human T lymphotropic virus type 1 (HTLV‐1) infects 10–20 million people worldwide. The majority of infected individuals are asymptomatic; however, approximately 3% develop the debilitating neurological disease HTLV‐1‐associated myelopathy/tropical spastic paraparesis (HAM/TSP). There is also currently no cure, vaccine or effective therapy for HTLV‐1 infection, and the mechanisms for progression to HAM/TSP remain unclear. NK T cells are an immunoregulatory T cell subset whose frequencies and effector functions are associated critically with immunity against infectious diseases. We hypothesized that NK T cells are associated with HAM/TSP progression. We measured NK T cell frequencies and absolute numbers in individuals with HAM/TSP infection from two cohorts on two continents: São Paulo, Brazil and San Francisco, CA, USA, and found significantly lower levels when compared with healthy subjects and/or asymptomatic carriers. Also, the circulating NK T cell compartment in HAM/TSP subjects is comprised of significantly more CD4⁺ and fewer CD8⁺ cells than healthy controls. These findings suggest that lower numbers of circulating NK T cells and enrichment of the CD4⁺ NK T subset are associated with HTLV‐1 disease progression.     

Spontaneous alloreactivity of natural killer (NK) and lymphokine-activated killer (LAK) cells from athymic rats against normal haemic cells. NK cells stimulate syngeneic but inhibit allogeneic haemopoiesis.

We wanted to re-examine the hypotheses that natural killer (NK) cells preferentially react with immature cells, and that they are not directed against major histocompatibility complex (MHC) gene products. Rat marrow cells could be separated according to maturity on a four-step discontinuous density gradient of Percoll. Almost all the immature bone marrow cells with progenitor activity, as measured in vivo in a diffusion chamber assay or in vitro in a granulocyte/macrophage colony-forming assay, resided within the lighter density cell fraction (density approximately 1.065). The higher density cells (density approximately 1.082) contained mainly the more mature, non-proliferative cells within the granulocyte series. NK and lymphokine-activated killer (LAK) cells from athymic rats, being devoid of T cells, efficiently killed low- as well as high-density bone marrow cells from a fully allogeneic and a MHC congenic rat strain, while little or no killing was observed against syngeneic bone marrow cell fractions. LAK cells also effectively inhibited granulocyte/macrophage colony formation from allogeneic bone marrow precursors in vitro, while stimulating colony formation from syngeneic bone marrow cells. The NK-mediated killing of allogeneic bone marrow cells was effectively inhibited by NK-sensitive tumour cells, while there was much less inhibition of the killing of tumour cells by allogeneic bone marrow cells. We conclude that NK cells recognize MHC incompatibilities on both immature and mature allogeneic bone marrow cells through recognition systems not related to T-cell receptors, and that allospecific killing can explain the contrasting effect of NK cells on allogeneic and syngeneic haematopoiesis.     

Hyperimmunoglobulinaemia, T-cell deficiency and plasmacytosis in RFM mice with host versus graft disease induced by the perinatal inoculations (T6XRFM)F1 spleen cells.

Host versus graft (HVG) syndrome may be induced in parental strain mice by perinatal inoculations of F1 hybrid spleen cells. The principal manifestations of the disease include thrombocytopaenia, intravascular fibrin deposits, intestinal haemorrhage, hepatic infarcts, lymphosplenomegaly and renal disease. Immune complexes have been shown to be the cause of the renal lesions, and have been implicated as the triggers for disseminated intravascular coagulation. In the present studies of RFM mice perinatally inoculated with (T6 x RFM)F1 spleen cells (RFM/(T6 x RFM)F1 mice), quantitative determinations of serum immunoglobulins (Ig) revealed marked elevations of IgG1, IgG2, IgA and IgM. Electrophoretic analyses revealed the polyclonal pattern which typically follows chronic antigenic stimulation. However, IgG1 levels which reached 29 to 72 times control values suggested disruption of homeostatic mechanisms which control circulating Ig levels. Because antibody responses to histocompatibility antigens were present only occasionally, and then in low titre, it seemed unlikely these antigens were the principal causes of hypergammaglobulinaemia and plasmacytosis. Morphological studies indicated that the elevated levels of Ig seen in end-stage HVG syndrome correlated well with marked plasmacytosis, the third morphological finding in a sequence that included the precocious development of germinal centres and subsequent depletion of thymic-dependent (T) lymphocytes. The fact that spleen cells from RFM/(T6 x RFM)F1 mice were severely impaired in their capacity to cause graft versus host disease in related (T6 x RFM)F1 and unrelated C3H mice provided strong evidence that the HVG reaction resulted in T-cell depletion, rather than specific immunoincompetence.     

Cloning of murine splenic T lymphocytes and natural killer (NK) cells on filter paper discs: detection of a novel NK/T phenotype.

Discrete colonies of splenocytes were grown on filter paper discs in the presence of concanavalin A and interleukin 2. Phenotypic analysis of the colonies indicated that the majority expressed the Thy-1.2 marker and 72% of these co-expressed the CD3 molecule. Of the colonies 20%-25% were NK 1.1+ and they developed regardless of the presence of Con A in the culture medium, a property of the NK lineage. In addition, Thy-1.2+ colonies developed when splenocytes from scid mice, which lack mature T and B cells, were grown both in the presence and absence of concanavalin A. These results demonstrate that colonies of murine splenic T lymphocytes and NK cells could be successfully grown on filter paper discs and phenotypically characterized. With this colonies technique, it was possible to identify a novel subset of NK 1.1+ colonies that co-expresses CD3 and shares growth properties with T cell colonies.     

Human natural killer (NK) cells present staphylococcal enterotoxin B (SEB) to T lymphocytes

Superantigen-mediated T cell activation requires the participation of antigen-presenting cells (APC). Once superantigen has bound class II MHC molecules on the surface of APC, it then can interact with the T cell receptor to induce T cell activation. Superantigen-mediated T lymphocyte activation, along with its consequent cytokine production is thought to be the basis for the pathophysiology of conditions such as toxic shock syndrome, Kawasaki''s disease and possibly rheumatoid arthritis. We examined the role of CD56⁺ NK lymphocytes in the interaction between superantigens and T lymphocytes. First, we found that a subpopulation of CD56⁺ cells freshly isolated from human peripheral blood expressed class II MHC molecules. The amount of HLA-DR expression varied between individuals, ranging from 9.3% to 37.7%. CD56⁺ (NK) cells were purified from the peripheral blood by cell sorting and were tested for their ability to support SEB-mediated T cell activation as assessed by surface expression of IL-2 receptor α-chain (CD25) on CD3⁺ lymphocytes. We observed that when enriched T cells were incubated with SEB in the presence of NK cells, there was a significant up-regulation of CD25 expression on the T cells. When HLA-DR⁺ cells were removed from sorted CD56⁺ populations, the remaining HLA-DR⁻ NK cells were unable to support SEB-mediated T cell activation. Also, SEB up-regulated the expression of HLA-DR on CD56⁺ cells in peripheral blood mononuclear cell (PBMC) populations after 24 h of incubation, implying that the ability of NK cells to function as superantigen-presenting cells is up-regulated by superantigens themselves. Together, these data demonstrate for the first time that human CD56⁺HLA-DR⁺ NK cells can function as superantigen-presenting cells, and imply that NK cells may be involved in the activation of non-specific T cell reactivity during early host defences against superantigen-elaborating microorganisms in vivo. Furthermore, the physical linkage of NK cells and T cells by the interaction of superantigen with HLA class II molecules and T cell receptors, respectively, may lead to NK cell activation and augmented lytic potential, helping to clear the body of superantigen-elaborating microorganisms.     

Different natural killer (NK) receptor expression and immunoglobulin E (IgE) regulation by NK1 and NK2 cells

Many studies concerning the role of T cells and cytokines in allergy have been performed, but little is known about the role of natural killer (NK) cells. Accordingly, the expression of co-stimulatory, inhibitory and apoptosis receptors, cytokine profiles and their effect on immunoglobulin isotypes were investigated in polyallergic atopic dermatitis (AD) patients with hyper immunoglobulin E (IgE) and healthy individuals. AD patients showed significantly decreased peripheral blood NK cells compared to healthy individuals. Freshly isolated NK cells of polyallergic patients spontaneously released higher amounts of interleukin (IL)-4, IL-5, IL-13 and interferon (IFN)-gamma compared to healthy individuals. NK cells were differentiated to NK1 cells by IL-12 and neutralizing anti-IL-4 monoclonal antibodies (mAb), and to NK2 cells by IL-4 and neutralizing anti-IL-12 mAb. Following IL-12 stimulation, NK cells produced increased levels of IFN-gamma and decreased IL-4. In contrast, stimulation of NK cells with IL-4 inhibited IFN-gamma, but increased IL-13, production. The effect of NK cell subsets on IgE regulation was examined in co-cultures of in vitro differentiated NK cells with peripheral blood mononuclear cells (PBMC) or B cells. NK1 cells significantly inhibited IL-4- and soluble CD40-ligand-stimulated IgE production; however, NK2 cells did not have any effect. The inhibitory effect of NK1 cells on IgE production was blocked by neutralization of IFN-gamma. Except for CD40, NK cell subsets showed different expression of killer-inhibitory receptors and co-stimulatory molecules between the polyallergic and healthy subjects. These results indicate that human NK cells show differences in numbers, surface receptor and cytokine phenotypes and functional properties in AD.     

Regulatory T cells and regulatory natural killer (NK) cells play important roles in feto-maternal tolerance

In the early pregnancy decidua, lymphocytes express some activation markers on their surface, suggesting that maternal lymphocytes are activated and recognize the semiallograftic fetus. Therefore, the immunoregulation system must work to prevent fetus rejection. Recent data showed that parts of the immunoregulation system such as CD4⁺CD25⁺ regulatory T (Treg) cells, Th3 cells, Tr1 cells, regulatory NK cells, and a tryptophan-catabolizing enzyme, indolamine 2,3 deoxygenase, play very important roles in the maintenance of pregnancy. Not only Treg cells but also regulatory NK cells may inhibit maternal T cell or NK cell fetal attack.     

Laminin inhibits the recognition of tumor target cells by murine natural killer (NK) and natural cytotoxic (NC) lymphocytes.

Tumor cells sensitive to lysis by murine natural killer (NK) or natural cytotoxic (NC) cells were shown to bind laminin. They bound 125I-labeled laminin in a time- and concentration-dependent manner, and binding of the radioactive laminin was inhibited by excess cold laminin. In the presence of laminin, cell-cell aggregation occurred. Murine tumor cells not sensitive to NK/NC-mediated killing bound much less laminin, and laminin did not induce aggregation of these cells. The addition of exogenous laminin to NK or NC cytotoxicity assays reduced target lysis in a dose-related manner. Reduction of lysis was due to an inability of NK/NC cells to bind to the targets. Target cells pretreated with laminin were reduced in their ability to cold-target compete for NK-mediated lysis of untreated target cells. These effects were unique to laminin. The control proteins (fibronectin and thyroglobulin) had no effect on NK activity. Finally, inhibition of cytolytic activity by laminin appeared to be specific for NK/NC cells. Laminin had no effect on cytolysis mediated by alloimmune cytotoxic T lymphocytes regardless of whether the targets did or did not bind laminin.     

Effects of tumour necrosis factor-alpha (TNF-alpha), IL-1 beta and monocytes on lymphokine-activated killer (LAK) induction from natural killer (NK) cells and T lymphocytes.

Roles of monocytes and cytokines were investigated on LAK induction from T and NK cells. Monocytes augmented more T-LAK induction than did NK-LAK. Expression of IL-1 beta, TNF-alpha and interferon-gamma (IFN-gamma)-mRNA and their cytokine production were superior in NK cells compared with T cells in parallel with their LAK activities. An increase of TNF-alpha, IL-1 beta and IFN-gamma production was induced by co-culturing NK or T cells with autologous monocytes. The augmentation of T cell cytokine production and T-LAK activity by monocytes was more prominent than that of NK cells. TNF-alpha and IL-1 beta were generated 24 h after IL-2 stimulation, and these cytokines were able to almost substitute for monocytes in LAK induction. Conversely, LAK induction was almost completely suppressed by both anti-IL-1 beta and anti-TNF-alpha antibodies, if they were added within 24 h after the start of the LAK induction. IFN-gamma, which was produced at a later stage, scarcely affected LAK induction in spite of the cooperation with TNF-alpha. The results obtained indicate conclusively that the superiority of NK-LAK depends on their superior productivity of both IL-1 beta and TNF-alpha, and that the up-regulation of LAK induction by monocytes is largely due to the enhanced generation of both cytokines.     

Differential regulation of GM1 and asialo-GM1 expression by T cells and natural killer (NK) cells in respiratory syncytial virus infection

We previously reported that respiratory syncytial virus (RSV) infection increases lung CD8(+) T cell GM1 expression. The related lipid asialo-GM1 (ASGM1) is expressed by T cells in viral infection and by natural killer (NK) cells. The in vivo co-expression of GM1 and ASGM1 by immune cells is not defined. Here we analyzed lung lymphocyte GM1 and ASGM1 expression in RSV-infected mice. GM1 and ASGM1 were coordinately upregulated by activated CD8(+) T cells in RSV-infected BALB/c and C57BL/6 mice. In contrast, RSV infection had no effect on constitutively high NK cell GM1 expression, while increasing NK cell ASGM1 expression. GM1 and ASGM1 co-localized in lipid raft structures in NK and CD8(+) T cells sorted from the lungs of RSV-infected mice. Anti-ASGM1 Ab treatment of RSV-infected BALB/c mice depleted GM1/ASGM1-expressing NK cells and GM1/ASGM1-expressing T cells, reduced lung IFN-gamma levels, increased viral load, delayed viral clearance, and reduced illness. STAT1(-/-) mice are more susceptible to RSV replication and disease than wild-type mice. In RSV-infected STAT1(-/-) mice, anti-ASGM1 Ab altered cytokine levels, but in contrast to BALB/c mice, antibody treatment had no effect on viral load or illness. Taken together, GM1 and ASGM1 expression are differentially regulated by T and NK cells in RSV infection. Also, GM1/ASGM1-expressing cells are important for control of RSV in BALB/c mice, whereas STAT1(-/-) mice clear RSV by an alternative pathway.     

CD1d-mediated antigen presentation to natural killer T (NKT) cells

CD1d molecules are lipid antigen-presenting molecules. They are involved in presenting these antigens to a unique subpopulation of T cells called natural killer T (NKT) cells, which have the capacity to produce both T helper (Th) 1 and Th2 cytokines. Thus, it is possible that the antigens presented by CD1d and/or the level at which they are presented could have profound effects on the immunoregulation of autoimmune and infectious diseases, as well as cancer. Because of the ability of CD1d-binding ligands to modulate NKT cell responses, targeting CD1d-mediated antigen presentation as a novel approach for new therapies in these and other diseases holds great promise.     

Natural killer (NK) cells and graft-versus-host disease (GVHD): no correlation between the NK cell levels and GVHD in the murine P----F1 model

Graft-versus-host disease (GVHD) was induced in (CBA X C57BL/6) F1 mice by i.v. injection of 50 X 10(6) parental spleen cells. The GVHD induced an enhanced NK (anti-YAC-1) cytotoxicity during the first 2 weeks after the spleen cell transfusion. This cytotoxic activity was shown to be mediated by asialo GM1-positive, partially Thy-1-positive and nylon-wool (NW) non-adherent cells, thus being classical NK cells. Depletion of NK-cell activity from donor and/or recipient mice with anti-asialo GM1 antibody prior to the spleen cell transfer did not prevent the GVHD as judged by the splenomegaly assay. Also, when NK activity was potentiated with polyinosinic-polycytidylic acid (pIC), no effect on the GVHD was seen. These data suggest that NK cells are not crucial for the development of GVHD in this model.     

Molecular profiling reveals distinct functional attributes of CD1d-restricted natural killer (NK) T cell subsets

CD1d-restricted natural killer T (NKT) cells can have multiple effects on an immune response, including the activation, regulation and attraction of innate immune cells, and modulation of adaptive immunity. Recent studies reveal that there are distinct subsets of NKT cells which selectively perform some of the functions attributed to CD1d-restricted cells, but the mechanisms underlying these functional differences have not been resolved. Our aim in this study was to identify novel NKT cell associated traits that would provide important insight into NKT cell activation and function. To this end, we have performed gene expression profiling of two separate subsets of NKT cells, analyzing genes differentially expressed in these cells compared to conventional CD4(+)NK1.1(-) T cells. We identify different sets of genes over expressed in each of the two NKT cell types, as well as genes that are common to the two CD1d-restricted NKT cell populations analyzed. A large number of these genes are highly relevant for NKT cell development, activation and function. Each NKT subtype displayed a unique set of chemokine receptors, integrins and molecules related to effector function, supporting the notion that distinct NKT cells can be selectively engaged and have diverse functions in different types of immune reactions.     

Graft-versus-host disease in recipients of grafts from natural killer T cell-deficient (Jalpha281(-/-)) donors

Valpha14i natural killer T cells (NKT cells) are a CD1-restricted subset of NKT cells that express an invariable Valpha14+ Jalpha281+ alphabeta T-cell receptor. To determine whether the absence of Valpha14i NKT cells from the graft affects the development of acute GVHD, we induced GVH reactions using Jalpha281(-/-) mice as donors in the C57BL/6-->(C57BL/6 x DBA/2)F1-hybrid strain combination. Recipients of grafts from Jalpha281(-/-) donors were not protected from either the morbidity or the severe wasting syndrome associated with the development of acute GVHD, but the concentrations of some T helper 1 (Th1) and Th2 cytokines were different from those seen in recipients of grafts from wild-type donors. Interferon-gamma was seen earlier (day 4) in recipients of grafts from Jalpha281(-/-) donors but did not reach the concentrations seen in recipients of grafts from wild-type donors on day 8 (P < 0.02). On day 8, the amount of tumour necrosis factor-alpha released into the serum following the injection of a small amount of lipopolysaccharide was lower in recipients of grafts from Jalpha281(-/-) donors (P < 0.02). The amount of interleukin (IL)-5 was also lower in recipients of grafts from Jalpha281(-/-) donors, when compared to the concentration seen in recipients of grafts from wild-type donors (P < 0.002). IL-13 was seen in recipients of grafts from Jalpha281(-/-) donors but not in recipients of grafts from wild-type donors. Our findings show that the absence of donor Valpha14i NKT cells is associated with lower concentrations of some Th1 cytokines. We also observed higher IL-13 concentrations and lower IL-5 concentrations in recipients of grafts from Jalpha281(-/-) donors indicating a variable effect on Th2 cytokine production.     

Selective expression of protein F1/(GAP-43) mRNA in pyramidal but not granule cells of the hippocampus

Protein F1/GAP-43 is a protein kinase C substrate associated with axonal growth and synaptic plasticity. We used in situ hybridization in rat brain to determine the cellular distribution of its gene expression. Throughout the septotemporal axis of the adult hippocampus, pyramidal cells express F1/GAP-43 mRNA, but granule cells do not. To determine if F1/GAP-43 expression in granule cells ever occurs, we studied its expression in development during mossy fiber outgrowth, when expression should be maximal. Quantitation of relative hybridization levels in the hippocampus revealed a modest increase in granule cell F1/GAP-43 mRNA coincident with mossy fiber outgrowth. But even the peak hybridization in granule cells on day 16 was 75% less than in pyramidal cells. The distribution of grains was over the entire granule cell layer at day 9, but was restricted by day 20 to the inner aspect of the layer, the site of the youngest cells which are still sending out axonal processes. Cell-selective expression of F1/GAP-43 within a particular brain structure was not restricted to the hippocampus. In cerebellum, F1/GAP-43 hybridization was detected in granule cells but not Purkinje cells; in olfactory bulb, mitral cells but not internal granule cells; in habenula, cells in the lateral but not medial nucleus; in substantia nigra, pars compacta cells but not cells in pars reticulata. Neurons containing biogenic amines exhibited intense F1/GAP-43 hybridization: substantia nigra pars compacta (dopamine), the locus coeruleus (norepinephrine), and dorsal raphe (serotonin). In contrast, cholinergic neurons exhibited little (basal forebrain) or no (medial habenula) hybridization. F1/GAP-43 expression is not restricted to a specific cell type and is not correlated with axon length. High F1/GAP-43 expression is apparent in many neurons having either neuromodulatory or memory storage functions. We propose that F1/GAP-43 is important for accelerating process outgrowth and synaptic remodeling, rather than directing growth itself.