Induction of calcium flux and enhancement of cytolytic activity in natural killer cells by cross-linking of the sheep erythrocyte binding protein (CD2) and the Fc-receptor (CD16)

Binding of the anti-cluster of differentiation (CD) 2 monoclonal antibody 9-1 causes an increase in the concentration of cytoplasmic-free calcium ([Ca2+]i) in cultured CD3-/CD16+ natural killer (NK) cells. This response did not occur in cultured CD3+/CD16- cytotoxic T lymphocytes (CTL). Anti-CD16 antibodies could partially block the calcium response when NK cells were stimulated with intact antibody 9-1, and antigen-binding fragment F(ab')2 of antibody 9-1 did not produce a calcium response. Thus an interaction of the 9-1 antibody with CD16 Fc receptors was required for the functional effect. The dual interaction of antibody 9-1 with both CD2 and CD16 was demonstrated by comodulation experiments. The cytolytic activity of cultured NK cells was increased by antibody 9-1 but not by F(ab')2 fragments of antibody 9-1. The enhanced lytic activity was blocked by anti-CD16 antibody, anti-CD18 antibody, and anti-CD2 antibodies that do not block the binding of antibody 9-1. This pattern was distinct from antibody-dependent cell-mediated cytotoxicity which was blocked only by the anti-CD16 antibody. Thus antibody 9-1 enhanced cytotoxicity by activating effector cells. There was no enhancement of lytic activity when F(ab')2 of antibody 9-1 were cross-linked with a polyclonal antiglobulin, even though [Ca2+]i was increased. These results show that induction of a [Ca2+]i response is not sufficient to enhance lytic activity in NK cells, and suggest that signals delivered through CD16 are necessary.

CD5 antibodies increase intracellular ionized calcium concentration in T cells

The binding of a variety of monoclonal antibodies to the CD5 (T, gp67) pan T cell differentiation antigen has been shown to potentiate T cell proliferation. In this paper we show that CD5 monoclonal antibodies cause increased intracellular free calcium concentration ([Ca2+]i) in T cells. An increase in [Ca2+]i occurred within 1 min in indo-1-loaded PBMC after the addition of CD5 monoclonal antibodies and cross-linking with a second step anti-mouse kappa light chain antibody. Cross-linking of CD5 was effective when done directly on the cell surface or by the administration of preformed soluble complexes that contained CD5 antibodies. Calcium mobilization induced by suboptimal concentrations of CD3 antibodies was specifically augmented and sustained by CD5 antibodies, although the enhancement was modest in magnitude. When cell surface phenotype was correlated with calcium mobilization, it was found that the CD5 response was restricted to CD5+/CD3+ cells, and that approximately 90% of CD5+ cells had responded. CD5-induced calcium mobilization was found to differ from CD3 stimulation in that EGTA entirely ablated the CD5 response, whereas the CD3 response was resistant to EGTA, indicating that the CD5-induced increased [Ca2+]i is derived primarily or entirely from extracellular calcium. CD5-stimulated calcium mobilization also differed from CD3 in that the CD5 response was inhibited by pretreatment with phorbol myristate acetate, whereas the CD3 response was not, suggesting that depletion of protein kinase C causes an uncoupling of signal transduction between CD5 and calcium channels. Finally, experiments were done with T cells after antigenic modulation of the CD3 or CD5 molecules. Unexpectedly, both the CD5 and the CD3 responses were ablated on CD3-modulated cells, whereas only the CD5 response was ablated on CD5-modulated cells. In addition, several Cd5+/CD3- T cell leukemia lines also failed to respond to CD5 stimulation, providing further evidence which indicates that the CD5 response depends on the cell surface expression of CD3 or a CD3-associated structure. These findings suggest that one mechanism for CD5-induced augmentation of mitogen-stimulated T cell proliferation involves increased [Ca2+]i which is distinct from but interdependent with that induced by stimulation of the CD3 molecule.

CD5 antibodies increase intracellular ionized calcium concentration in T cells

The binding of a variety of monoclonal antibodies to the CD5 (T, gp67) pan T cell differentiation antigen has been shown to potentiate T cell proliferation. In this paper we show that CD5 monoclonal antibodies cause increased intracellular free calcium concentration ([Ca2+]i) in T cells. An increase in [Ca2+]i occurred within 1 min in indo-1-loaded PBMC after the addition of CD5 monoclonal antibodies and cross-linking with a second step anti-mouse kappa light chain antibody. Cross-linking of CD5 was effective when done directly on the cell surface or by the administration of preformed soluble complexes that contained CD5 antibodies. Calcium mobilization induced by suboptimal concentrations of CD3 antibodies was specifically augmented and sustained by CD5 antibodies, although the enhancement was modest in magnitude. When cell surface phenotype was correlated with calcium mobilization, it was found that the CD5 response was restricted to CD5+/CD3+ cells, and that approximately 90% of CD5+ cells had responded. CD5-induced calcium mobilization was found to differ from CD3 stimulation in that EGTA entirely ablated the CD5 response, whereas the CD3 response was resistant to EGTA, indicating that the CD5-induced increased [Ca2+]i is derived primarily or entirely from extracellular calcium. CD5-stimulated calcium mobilization also differed from CD3 in that the CD5 response was inhibited by pretreatment with phorbol myristate acetate, whereas the CD3 response was not, suggesting that depletion of protein kinase C causes an uncoupling of signal transduction between CD5 and calcium channels. Finally, experiments were done with T cells after antigenic modulation of the CD3 or CD5 molecules. Unexpectedly, both the CD5 and the CD3 responses were ablated on CD3-modulated cells, whereas only the CD5 response was ablated on CD5-modulated cells. In addition, several Cd5+/CD3- T cell leukemia lines also failed to respond to CD5 stimulation, providing further evidence which indicates that the CD5 response depends on the cell surface expression of CD3 or a CD3-associated structure. These findings suggest that one mechanism for CD5-induced augmentation of mitogen-stimulated T cell proliferation involves increased [Ca2+]i which is distinct from but interdependent with that induced by stimulation of the CD3 molecule.

Crosslinking of surface antigens causes mobilization of intracellular ionized calcium in T lymphocytes

Antibodies binding to a large subset of T-cell differentiation antigens, including CD2, CD4, CD5, CD6, CD7, CD8, Tp44, and CDw18, cause an increase in the cytoplasmic calcium concentration [( Ca2+]i) after the antigens are crosslinked on the cell surface. Similar crosslinking-induced signals were seen for a subset of mouse thymocyte differentiation antigens. The various antigens on human T cells differed in the extent of crosslinking required for generating the calcium signal, as evidenced by comparisons with monoclonal versus polyclonal second-step antibody. The [Ca2+]i increase that occurs after crosslinking represents mobilization of cytoplasmic calcium since the initial component of the signal is resistant to depletion of extracellular calcium by chelation with EGTA. The [Ca2+]i increase is completely inhibited by pretreatment of cells with pertussis toxin, indicating that a substrate for pertussis toxin regulates the signal transduction. Crosslinking of antigens other than the CD3/T-cell receptor complex did not result in T-cell proliferation. Crosslinking of CD2 and Tp44, but not other antigens, resulted in expression of functional interleukin 2 receptors. Comparisons of three different anti-CD3 antibodies showed that a second calcium signal was generated by crosslinking, even when the anti-CD3 antibodies were used at optimal concentrations.

Stimulation of T cells through the CD3/T-cell receptor complex: role of cytoplasmic calcium, protein kinase C translocation, and phosphorylation of pp60c-src in the activation pathway

Stimulation of T cells or the Jurkat T-cell line with soluble antibodies to the CD3/T-cell receptor complex causes mobilization of cytoplasmic Ca2+, which is blocked by pertussis toxin but not by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and translocation of protein kinase C activity from the cytoplasm to the membrane. Such stimulation also causes phosphorylation of pp60c-src at an amino-terminal serine residue. These activities are consistent with induction of phosphatidylinositol metabolism after antibody binding. Anti-CD3 stimulation with antibody in solution, however, does not cause Jurkat cells to release interleukin 2 and blocks rather than induces proliferation of T cells. Induction of interleukin 2 production by Jurkat cells and proliferation by normal T cells requires anti-CD3 stimulation with antibody on a solid support, such as Sepharose beads or a plastic dish. Thus, we examined phosphorylation of pp60c-src after stimulation of Jurkat cells with anti-CD3 in solution or on solid phase. Both of these caused serine phosphorylation of pp60c-src that was indistinguishable even after 4 h of stimulation. These results indicate that the mode of anti-CD3 stimulation (in solution or on solid phase) controls a cellular function that modifies the consequences of signal transduction through phosphatidylinositol turnover.

Antibody binding to CD5 (Tp67) and Tp44 T cell surface molecules: effects on cyclic nucleotides, cytoplasmic free calcium, and cAMP-mediated suppression

T cells can be activated to proliferate by antibodies to the T cell antigen receptor or the molecularly associated CD3 complex if monocytes are present. We have shown previously that monoclonal antibodies to the human T cell differentiation antigens CD5 (Tp67) and Tp44 each augment and prolong proliferative responses of anti-CD3-activated T cells, even in the absence of monocytes. Here we show that the functional and biochemical mechanisms of CD5 and Tp44 signal transmission are distinct. T cell proliferation is suppressed by agents that increase the concentration of intracellular cAMP. We found that antibody binding to the Tp44 surface molecule overcomes this suppression, whereas antibody binding to CD5 does not, indicating that ligand-Tp44 interaction changes T cell sensitivity to cAMP-mediated growth inhibition. The ability of anti-CD3, anti-Tp44, and anti-CD5 monoclonal antibodies to directly alter cyclic nucleotide levels in the Jurkat T cell line was examined. Anti-CD3 alone caused a rapid four- to sixfold increase in cAMP levels, but did not affect cGMP levels. However, anti-Tp44 and anti-CD5 each caused a rapid three- to fourfold increase in cGMP levels without affecting cAMP levels. In other experiments, cytoplasmic free calcium levels were measured in resting T cells after CD5 or Tp44 stimulation by using the dye indo-1 and flow cytometry. This sensitive method showed that anti-CD5 alone caused an increase in cytoplasmic calcium free levels within 3 min of antibody addition, whereas anti-Tp44 had no effect. Finally, anti-Tp44 and IL 1 each augmented proliferation of phorbol ester-stimulated lymphocytes, whereas anti-CD5 did not. The effects of IL 1 and Tp44 could be further distinguished in that the effect of anti-Tp44 was resistant to inhibition by dBcAMP whereas IL 1 was not. These data suggest that the receptor function of both Tp44 and CD5 involves changes in cyclic nucleotides levels, and that the mechanism by which anti-Tp44 and anti-CD5 antibodies affect T cell proliferative responses may be related to their selective effects on cGMP levels and cytoplasmic calcium concentrations.

Antibody binding to CD5 (Tp67) and Tp44 T cell surface molecules: effects on cyclic nucleotides, cytoplasmic free calcium, and cAMP-mediated suppression

T cells can be activated to proliferate by antibodies to the T cell antigen receptor or the molecularly associated CD3 complex if monocytes are present. We have shown previously that monoclonal antibodies to the human T cell differentiation antigens CD5 (Tp67) and Tp44 each augment and prolong proliferative responses of anti-CD3-activated T cells, even in the absence of monocytes. Here we show that the functional and biochemical mechanisms of CD5 and Tp44 signal transmission are distinct. T cell proliferation is suppressed by agents that increase the concentration of intracellular cAMP. We found that antibody binding to the Tp44 surface molecule overcomes this suppression, whereas antibody binding to CD5 does not, indicating that ligand-Tp44 interaction changes T cell sensitivity to cAMP-mediated growth inhibition. The ability of anti-CD3, anti-Tp44, and anti-CD5 monoclonal antibodies to directly alter cyclic nucleotide levels in the Jurkat T cell line was examined. Anti-CD3 alone caused a rapid four- to sixfold increase in cAMP levels, but did not affect cGMP levels. However, anti-Tp44 and anti-CD5 each caused a rapid three- to fourfold increase in cGMP levels without affecting cAMP levels. In other experiments, cytoplasmic free calcium levels were measured in resting T cells after CD5 or Tp44 stimulation by using the dye indo-1 and flow cytometry. This sensitive method showed that anti-CD5 alone caused an increase in cytoplasmic calcium free levels within 3 min of antibody addition, whereas anti-Tp44 had no effect. Finally, anti-Tp44 and IL 1 each augmented proliferation of phorbol ester-stimulated lymphocytes, whereas anti-CD5 did not. The effects of IL 1 and Tp44 could be further distinguished in that the effect of anti-Tp44 was resistant to inhibition by dBcAMP whereas IL 1 was not. These data suggest that the receptor function of both Tp44 and CD5 involves changes in cyclic nucleotides levels, and that the mechanism by which anti-Tp44 and anti-CD5 antibodies affect T cell proliferative responses may be related to their selective effects on cGMP levels and cytoplasmic calcium concentrations.

Heterogeneity among T cells in intracellular free calcium responses after mitogen stimulation with PHA or anti-CD3. Simultaneous use of indo-1 and immunofluorescence with flow cytometry

Measurement of intracellular ionized calcium concentrations ([Ca2+]i) has been indispensable in elucidating the central role of [Ca2+]i as a trigger of cellular responses to activating stimuli. Such studies have employed the dye quin2, which has not been readily adapted to analysis of individual small cells. We show here that the calcium response of large numbers of single cells can be analyzed with the use of flow cytometry and the recently described dye, indo-1. Such analyses demonstrate for the first time the heterogeneous nature of the [Ca2+]i response to mitogenic stimuli within populations of peripheral blood lymphocytes (PBL). By simultaneous quantitation of one- or two-color surface immunofluorescence labels, some of this heterogeneity of [Ca2+]i response in PBL is shown to be related to cellular immunophenotype. Almost all T cells responded to anti-CD3 antibody; however, the response is greater among CD4+ than CD8+ cells, and within the CD4+ population the rate of response to stimulation by antibody to CD3 differed between subpopulations defined by expression of the common leukocyte marker p220. In contrast, not all T cells responded to phytohemagglutinin (PHA), even at very high doses. As with anti-CD3, after stimulation with PHA, CD4+ cells showed a larger proportion of responding cells than did CD8+ cells. In separate experiments, indo-1 was found not to impair reproductive viability of PBL, thereby providing the potential for analysis of functional activity after the separation of cells by sorting on the basis of the [Ca2+]i response to stimuli. Mixing experiments indicated that a response of a subpopulation representing as little as 0.3% of total cells could be readily detected. Thus, the flow cytometric assay with indo-1 is the first technique that allows the quantitative analysis of response differences of small subpopulations of cells and intercellular variation in [Ca2+]i.

Heterogeneity among T cells in intracellular free calcium responses after mitogen stimulation with PHA or anti-CD3. Simultaneous use of indo-1 and immunofluorescence with flow cytometry

Measurement of intracellular ionized calcium concentrations ([Ca2+]i) has been indispensable in elucidating the central role of [Ca2+]i as a trigger of cellular responses to activating stimuli. Such studies have employed the dye quin2, which has not been readily adapted to analysis of individual small cells. We show here that the calcium response of large numbers of single cells can be analyzed with the use of flow cytometry and the recently described dye, indo-1. Such analyses demonstrate for the first time the heterogeneous nature of the [Ca2+]i response to mitogenic stimuli within populations of peripheral blood lymphocytes (PBL). By simultaneous quantitation of one- or two-color surface immunofluorescence labels, some of this heterogeneity of [Ca2+]i response in PBL is shown to be related to cellular immunophenotype. Almost all T cells responded to anti-CD3 antibody; however, the response is greater among CD4+ than CD8+ cells, and within the CD4+ population the rate of response to stimulation by antibody to CD3 differed between subpopulations defined by expression of the common leukocyte marker p220. In contrast, not all T cells responded to phytohemagglutinin (PHA), even at very high doses. As with anti-CD3, after stimulation with PHA, CD4+ cells showed a larger proportion of responding cells than did CD8+ cells. In separate experiments, indo-1 was found not to impair reproductive viability of PBL, thereby providing the potential for analysis of functional activity after the separation of cells by sorting on the basis of the [Ca2+]i response to stimuli. Mixing experiments indicated that a response of a subpopulation representing as little as 0.3% of total cells could be readily detected. Thus, the flow cytometric assay with indo-1 is the first technique that allows the quantitative analysis of response differences of small subpopulations of cells and intercellular variation in [Ca2+]i.

Valency of CD3 binding and internalization of the CD3 cell-surface complex control T cell responses to second signals: distinction between effects on protein kinase C, cytoplasmic free calcium, and proliferation

We have studied the relationship of valency of CD3 stimulation and modulation of the CD3 receptor complex with biochemical and proliferative responses of T cells. Anti-CD3 Fab, as well as F(ab')2 and whole antibody caused rapid modulation of the CD3 antigen, whereas anti-CD3 conjugated to Sepharose did not. In the absence of monocytes, T cells stimulated with anti-CD3 Fab, F(ab')2, or F(ab')2-Sepharose showed differences in their ability to respond to second signals given by PMA, IL 1, IL 2, or antibodies to Tp67 and Tp44. None of the anti-CD3 signals alone caused resting T cells to produce IL 2, and only the Sepharose-bound anti-CD3 F(ab')2 caused T cells to express high levels of functional IL 2 receptors. Anti-CD3 F(ab')2-Sepharose-stimulated T cells produced IL 2 and proliferated in response to each of the second signals. Because anti-CD3-Sepharose did not cause modulation of the CD3 antigen, the ability of the Sepharose-bound antibody to induce T cells to express IL 2 receptors and to respond to individual second signals may be related to lack of modulation rather than valency of binding. Anti-CD3 Fab-stimulated T cells responded to PMA but required combinations of other second signals. T cells stimulated with unmodified anti-CD3 antibody or F(ab')2 fragments responded to PMA but did not respond to any other second signals alone or in combination. Stimulations that resulted in modulation (i.e., anti-CD3 whole antibody, anti-CD3 F(ab')2, or anti-CD3 Fab fragments) caused an increase in cytoplasmic calcium levels in resting T cells but blocked proliferation of T cells in response to mitogenic lectins or CD2 stimulation. Anti-CD3 F(ab')2 on Sepharose, however, did not block T cell proliferation. Whole bivalent anti-CD3 antibody or F(ab')2 fragments, but not monovalent Fab fragments, caused a rapid translation of protein kinase C activity from cytosol to membrane in the Jurkat T cell line. Because all of these modulate the receptor, these data indicate that the functional difference between monovalent and bivalent binding to CD3 is related to antibody valency and not to antigenic modulation. The use of Fab anti-CD3 stimulation that requires combinations of second signals for proliferation allowed an analysis of the functional relationships between IL 1, anti-Tp67, and anti-Tp44.

Valency of CD3 binding and internalization of the CD3 cell-surface complex control T cell responses to second signals: distinction between effects on protein kinase C, cytoplasmic free calcium, and proliferation

We have studied the relationship of valency of CD3 stimulation and modulation of the CD3 receptor complex with biochemical and proliferative responses of T cells. Anti-CD3 Fab, as well as F(ab')2 and whole antibody caused rapid modulation of the CD3 antigen, whereas anti-CD3 conjugated to Sepharose did not. In the absence of monocytes, T cells stimulated with anti-CD3 Fab, F(ab')2, or F(ab')2-Sepharose showed differences in their ability to respond to second signals given by PMA, IL 1, IL 2, or antibodies to Tp67 and Tp44. None of the anti-CD3 signals alone caused resting T cells to produce IL 2, and only the Sepharose-bound anti-CD3 F(ab')2 caused T cells to express high levels of functional IL 2 receptors. Anti-CD3 F(ab')2-Sepharose-stimulated T cells produced IL 2 and proliferated in response to each of the second signals. Because anti-CD3-Sepharose did not cause modulation of the CD3 antigen, the ability of the Sepharose-bound antibody to induce T cells to express IL 2 receptors and to respond to individual second signals may be related to lack of modulation rather than valency of binding. Anti-CD3 Fab-stimulated T cells responded to PMA but required combinations of other second signals. T cells stimulated with unmodified anti-CD3 antibody or F(ab')2 fragments responded to PMA but did not respond to any other second signals alone or in combination. Stimulations that resulted in modulation (i.e., anti-CD3 whole antibody, anti-CD3 F(ab')2, or anti-CD3 Fab fragments) caused an increase in cytoplasmic calcium levels in resting T cells but blocked proliferation of T cells in response to mitogenic lectins or CD2 stimulation. Anti-CD3 F(ab')2 on Sepharose, however, did not block T cell proliferation. Whole bivalent anti-CD3 antibody or F(ab')2 fragments, but not monovalent Fab fragments, caused a rapid translation of protein kinase C activity from cytosol to membrane in the Jurkat T cell line. Because all of these modulate the receptor, these data indicate that the functional difference between monovalent and bivalent binding to CD3 is related to antibody valency and not to antigenic modulation. The use of Fab anti-CD3 stimulation that requires combinations of second signals for proliferation allowed an analysis of the functional relationships between IL 1, anti-Tp67, and anti-Tp44.

A 44 kilodalton cell surface homodimer regulates interleukin 2 production by activated human T lymphocytes

We previously described a cell surface antigen, termed Tp44, detected by monoclonal antibody 9.3 on approximately 80% of mature human T lymphocytes. Analysis by SDS-polyacrylamide gel electrophoresis and isoelectric focusing demonstrated that this antigen consists of two identical 44 kilodalton glycopeptides that form a disulfide-linked homodimer. Competitive binding experiments showed that antibody 9.3 and an anti-CD3 antibody (64.1) recognize distinct antigenic determinants; furthermore, the binding of antibody 9.3 was unaffected by prior modulation of CD3. Thus, Tp44 has no detectable cell surface association with CD3. By itself, antibody 9.3 had no detectable effect on either IL 2 receptor expression or IL 2 release, and did not cause T cell proliferation even when monocytes were present and exogenous IL 2 was provided, indicating that binding of antibody 9.3 does not provide a primary signal for T cell activation. However, the proliferative responses of T lymphocytes activated by phytohemagglutinin, concanavalin A, or an anti-CD3 monoclonal antibody were strikingly enhanced in the presence of antibody 9.3, an effect associated with increased IL 2 receptor expression and increased IL 2 secretion. Antibody 9.3 enabled anti-CD3-Sepharose-activated T cells and anti-CD3 antibody-activated Jurkat cells to release IL 2 in the absence of monocytes. Fab fragments of antibody 9.3 had no effect on anti-CD3-induced IL 2 release by Jurkat cells, whereas F(ab')2 fragments had activity comparable to that of unmodified antibody, indicating that bivalent binding of Tp44 molecules is required for IL 2 secretion. Together, these results suggest that TP44 may function as a receptor for accessory signals in the activation of T cells.

A 44 kilodalton cell surface homodimer regulates interleukin 2 production by activated human T lymphocytes

We previously described a cell surface antigen, termed Tp44, detected by monoclonal antibody 9.3 on approximately 80% of mature human T lymphocytes. Analysis by SDS-polyacrylamide gel electrophoresis and isoelectric focusing demonstrated that this antigen consists of two identical 44 kilodalton glycopeptides that form a disulfide-linked homodimer. Competitive binding experiments showed that antibody 9.3 and an anti-CD3 antibody (64.1) recognize distinct antigenic determinants; furthermore, the binding of antibody 9.3 was unaffected by prior modulation of CD3. Thus, Tp44 has no detectable cell surface association with CD3. By itself, antibody 9.3 had no detectable effect on either IL 2 receptor expression or IL 2 release, and did not cause T cell proliferation even when monocytes were present and exogenous IL 2 was provided, indicating that binding of antibody 9.3 does not provide a primary signal for T cell activation. However, the proliferative responses of T lymphocytes activated by phytohemagglutinin, concanavalin A, or an anti-CD3 monoclonal antibody were strikingly enhanced in the presence of antibody 9.3, an effect associated with increased IL 2 receptor expression and increased IL 2 secretion. Antibody 9.3 enabled anti-CD3-Sepharose-activated T cells and anti-CD3 antibody-activated Jurkat cells to release IL 2 in the absence of monocytes. Fab fragments of antibody 9.3 had no effect on anti-CD3-induced IL 2 release by Jurkat cells, whereas F(ab')2 fragments had activity comparable to that of unmodified antibody, indicating that bivalent binding of Tp44 molecules is required for IL 2 secretion. Together, these results suggest that TP44 may function as a receptor for accessory signals in the activation of T cells.

Monoclonal antibody-defined functional epitopes on the adhesion-promoting glycoprotein complex (CDw18) of human neutrophils

We have evaluated the functional and immunochemical activities of three monoclonal antibodies (MoAbs) minimally reactive with adherence-defective neutrophils (PMN) from a patient with recurrent bacterial infections. In studies with normal PMN, MoAbs OKM1 and 60.1 both precipitate the same 165kd alpha-subunit (alpha M) within an alpha-beta heterodimer complex (CD11). The CD11 complex is part of a larger complex composed of four glycoproteins (CDw18) precipitated by MoAb 60.3, with properties suggesting that the CDw18 complex is equivalent to the Mac-1, LFA-1, p150, 95 glycoprotein family implicated in adherence-dependent leukocyte functions. PMN adherence to endothelium, spreading on surfaces, aggregation, and phagocytosis of zymosan particles were all inhibited in a dose-dependent fashion by MoAb 60.1 (analogous to previous studies with MoAb 60.3) while MoAb OKM1 had no effect. These findings unify previously disparate observations and suggest that a functionally active site on the adherence promoting glycoprotein complexes CD11 and CDw18 is distant from the alpha M epitope recognized by MoAb OKM1 but closely associated with the alpha M epitope recognized by MoAb 60.1 and the beta-epitope (or epitope created by alpha-beta quaternary structure) recognized by MoAb 60.3.

Disseminated Fusarium moniliforme infection after allogeneic marrow transplantation

We have described the first case of systemic Fusarium moniliforme infection complicating marrow transplantation. The infection was fulminant despite aggressive therapy. Review of previously reported cases of human Fusarium infection suggests that the skin is a common portal of infection.

Distinct patterns of transmembrane calcium flux and intracellular calcium mobilization after differentiation antigen cluster 2 (E rosette receptor) or 3 (T3) stimulation of human lymphocytes

We evaluated CD2 (E rosette) and CD3 (T3)-triggered activation of resting lymphocytes by measuring the intracellular free calcium concentration ([Ca2+]i) of individual cells. The [Ca2+]i of indo-1-loaded cells was measured by flow cytometry and responses were correlated with cell surface phenotype. Stimulation with anti-CD3 antibody caused an increase in [Ca2+]i in greater than 90% of CD3+ cells within 1 min, and furthermore, the response was restricted to cells bearing the CD3 marker. In contrast, stimulation of cells with anti-CD2 antibodies produced a biphasic response pattern with an early component in CD3- cells and a late component in CD3+ cells. Thus, the CD2 response does not require cell surface expression of CD3. In addition, stimulation of a single CD2 epitope was sufficient for activation of CD3- cells, whereas stimulation of two CD2 epitopes was required for activation of CD3+ cells. Both the CD2 and CD3 responses were diminished in magnitude and duration by EGTA. However, approximately 50% of T cells still had a brief response in the presence of EGTA, indicating that the increased [Ca2+]i results in part from intracellular calcium mobilization, and furthermore demonstrates that extracellular calcium is required for a full and sustained response. Our results support the concept that CD2 represents the trigger for a distinct pathway of activation both for T cells that express the CD3 molecular complex and for large granular lymphocytes that do not.

Correlation of hypomagnesemia with the onset of cyclosporine-associated hypertension in marrow transplant patients

Cyclosporine is known to cause hypertension, and we have recently reported that it causes hypomagnesemia and renal magnesium wasting in marrow transplant recipients. We performed a case-control study to ask whether hypomagnesemia might be related to this form of drug-induced hypertension. The charts of 188 patients treated with cyclosporine were evaluated for the development of hypertension. The 32 patients who became hypertensive were age, sex, and disease-matched with 32 cyclosporine-treated controls. Baseline serum Mg levels were normal in both groups. However at the time of development of hypertension, the hypertensive patients had a mean (+/- SD) Mg of 1.22 +/- 0.20 mEq/L versus controls 1.40 +/- 0.33 mEq/L (P less than 0.01). Serum calcium, albumin, creatinine, potassium, and cyclosporine concentrations were not different between the two groups. This study may indicate that hypertension and hypomagnesemia are coincident toxicities in cyclosporine-treated patients. Alternatively, our data support the hypothesis that acquired derangements in magnesium metabolism may contribute to the development of hypertension. Magnesium replacement may prove beneficial in the treatment and/or prevention of cyclosporine-associated hypertension.

Ultrasonography and computed tomography in severe urinary tract infection

A prospective study evaluated the utility of renal computed tomography (CT) and ultrasonography in 35 patients hospitalized for treatment of urinary tract infection. Renal computed tomograms were abnormal in 18 of 28 patients with acute pyelonephritis and three of four patients with urosepsis, showing findings consistent with pyelonephritis in 17 patients and intrarenal abscess or focal bacterial nephritis in four patients. Renal sonograms were abnormal in only eight patients, showing findings compatible with pyelonephritis in four and intrarenal abscess or focal bacterial nephritis in the other four. Flank tenderness was absent in only four patients with CT findings of pyelonephritis, of whom three were diabetic. We therefore found that (1) renal CT is a sensitive test for acute upper urinary tract infection, (2) ultrasonography detects focal bacterial nephritis and abscesses but is insensitive to uncomplicated upper urinary tract infection, and (3) painless pyelonephritis may be more common in patients with diabetes mellitus.

Profound hypomagnesemia and renal magnesium wasting associated with the use of cyclosporine for marrow transplantation

We prospectively studied 41 marrow transplant patients to evaluate the possible association of hypomagnesemia with cyclosporine immunosuppressive therapy. During the 3 months posttransplant the mean nadir serum magnesium level was 1.06 +/- 0.16 mEq/L in 24 patients treated with cyclosporine and 1.33 +/- 0.13 in 14 patients treated with methotrexate (P less than 0.0001). Eleven of 24 patients receiving cyclosporine versus 1 of 14 patients receiving methotrexate had magnesium levels less than 1 mEq/L, or were begun on replacement therapy for presumed symptomatic hypomagnesemia (P less than 0.02). Agents known to be associated with hypomagnesemia, aminoglycosides and amphotericin B, were given in both lesser quantity and frequency to cyclosporine-treated patients than to methotrexate-treated patients. Hypomagnesemic patients treated with cyclosporine had inappropriately elevated urine magnesium excretion. Renal magnesium wasting may be added to the spectrum of nephrotoxicity resulting from cyclosporine. Several adverse reactions previously attributed to cyclosporine may be secondary to magnesium deficiency.

Association between cyclosporin neurotoxicity and hypomagnesaemia

The serum magnesium levels of all 12 allogeneic bone-marrow transplant recipients who experienced the neurotoxic effects of cyclosporin (CyA) were more than two standard deviations below the normal range. The neurological events seemed to segregate into three separate syndromes. 7 patients had grand-mal seizures, which occurred within the first several weeks of CyA therapy (median onset 12 days). At the time of their first seizure all 7 patients had hypomagnesaemia, which had developed rapidly over the preceding 1-3 weeks. 3 patients had four episodes of cerebellar ataxia, tremor, and depression. These subacute episodes developed after prolonged CyA therapy (median onset 67 days). Each episode was associated with hypomagnesaemia. 2 patients had a transient episode of expressive aphasia following a long period of hypomagnesaemia. In all cases symptoms resolved or did not recur with adequate magnesium replacement. These data suggest that CyA neurotoxicity is associated with hypomagnesaemia and may be treated or prevented with magnesium replacement.

Immunopathological aspects of Plasmodium berghei infection in five strains of mice. II. Immunopathology of cerebral and other tissue lesions during the infection

Histological changes during the course of P. berghei infection were investigated in A/J, BALB/c, OF1, CBA and C57B1 mice. The findings were studied in relation to serological aspects (Contreras et al., 1980). High mortality and acute deaths occurred in A/J, BALB/c and OF1 mice and marked cerebral lesions were found in these strains from day 15, including congestion of meningeal and cerebral veins and capillaries, blocking of these vessels by heavily parasitized RBC, cerebral oedema and haemorrhages. Such lesions were minimal in CBA and C57B1 mice, and absent in mice examined 21 and 24 days after infection. Small deposits of IgG and traces of C3 were detected by immunofluorescence in the choroid plexus of most mice from day 9. Renal lesions included congestion, plugging of veins and capillaries, low-grade mononuclear infiltration and mesangial thickening; these changes were most marked in CBA, C57B1 and A/J mice. Glomerular deposits of IgM were present in all strains in the first week of infection. IgG and C3 were detected in the second week, but only traces were found in CBA mice. The livers showed congestion, accumulation of pigment in swollen Kupffer cells and mononuclear portal infiltration; these were most pronounced in A/J mice. In the spleen, there was a great increase in the reticuloendothelial cell population, white pulp proliferation, congestion and accumulation of pigment and plasma cell reaction; the pattern of white pulp expansion varied in the different strains. The results suggest that cerebral lesions play a significant role in the aetiology of acute deaths in this malaria model.