A comparative study of the immunohistochemical localization of basic protein to myelin and oligodendrocytes in rat and chicken brain

Antisera to highly purified basic protein (BP) from rat and chicken brain were prepared and their purity and specificity demonstrated by double immunodiffusion and cross-immunoadsorption. These antisera were used for immunohistochemical localization of BP in the brains of adult and developing rat and chick. Myelin basic protein was exclusively localized to myelin or the myelin forming elements of the CNS. It was present in high concentrations in white matter and absent in areas free of myelin. Neuronal parikarya and dendrites were negative as were axons cut in cross section and at Nodes of Ranvier. The latter was best observed in cross sections of human spinal cord demonstrating also the immunoreactivity of the antibodies with human BP. The internodal distance in a fine (1.5 micrometer) rat cortical fiber was determined to be approximately 45 micrometers. Myelin basic protein was shown to extend into cranial roots, in contrast to myelin proteolipid protein which abruptly lose fluorescence as the nerves emerged from the brain. During development, BP was first observed on the fourteenth day of incubation in chick and at birth in the rat. The protein appeared in oligodendrocytes and in association with fibers near these cells. Fluorescent processes were frequently observed connecting the oligodendrocytes with the fibers. As myelination progressed, the intensity of the immunohistochemical reaction decreased in the oligodendrocytes while the brightness in fibers increase. Eventually, the oligodendrocytes became undetectable. Fibers with immature myelin exhibited a beaded or varicosed appearance with the highest concentration of immunofluorescence in the outer portion of the varicosities. The varicosities were postulated to represent dilations in the newly forming sheath between intervals of compaction along the axon undergoin myelination. These dilations might represent areas of increased cytoplasmic volume which could serve as channels for transport and/or storage sites for myelin proteins prior to incorporation into the membrane. The varicosities became less prominent with the thickening of the myelin sheath and mature myelinated fibers became smooth. The process of synthesis of BP, transport of the protein to the varicosed fibers, and maturation of the myelin sheath was seen to progress in a more or less caudal to rostral direction as myelination of the CNS takes place. In the rat, this was accomplished over approximately a 30-day period starting near the time of birth. In the chick, most of the myelination was accomplished in the three or four days immediately before hatching. At this time, innumerable oligodendrocytes were observed producing BP simultaneously in the major white fiber tracts. It is postulated that in chick some degree of oligodendrocytic cell death occurs normally during myelination.

Antibody and complement modulation of tumor cell growth in vitro and in vivo

Low doses of highly purified anti-TNP (trinitrophenyl) antibody specifically stimulated nucleoside uptake in TNP-substituted L cells and low doses of heterospecific anti-L cell antibody stimulated nucleoside incorporation, DNA synthesis, and cell growth in L cells in vitro. High concentrations of antibody inhibited these processes. Complement activated through C3 augmented the cytostimulatory effects of low concentrations of antibody and activated through C9 augmented the cytoinhibitory effects of antibody. One very early effect of cytostimulatory concentrations of antibody is activation of membrane carrier transport systems as seen with 45Ca2+ uptake. Growth of L cells in tissue culture in the continuous presence of a cytostimulatory concentration of antibody selected for a variant cell line that was less responsive to antibody, thought to be due to a blocking effect of increased amounts of sialic acid. In vivo experiments documented that the same antibody could modulate L cell tumor growth in T cell-depleted mice, depending on whether a low or high concentration of antibody was given passively. In the experimental systems used, therefore, antitumor antibody and complement directly modulate the growth of tumor cells.

Synthesis of DNA and poly(adenosine diphosphate ribose) in normal and chronic lymphocytic leukemia lymphocytes

Peripheral blood lymphocytes were isolated from 9 patients with chronic lymphocytic leukemia (CLL) and 12 normal control donors. The cells were assayed for synthesis of DNA and poly-(adenosine diphosphate ribose) (poly[ADPR]) immediately after isolation and on successive days following their treatment with phytohemagglutinin (PHA). Two different techniques were used to measure DNA synthesis. In the standard technique, DNA synthesis was measured by incubating intact cells with [(3)H]deoxythymidine. In the new technique, the lymphocytes were first rendered permeable to nucleotides, then DNA synthesis was measured by incubating them with [(3)H]deoxythymidine triphosphate in the presence of deoxyATP, deoxyGTP, deoxyCTP, ATP, and Mg(++). Both assays showed the anticipated rise in DNA synthesis after PHA stimulation of normal cells. PHA-stimulated lymphocytes from patients with CLL demonstrated low levels of DNA synthesis in both assay systems. The initial levels of poly(ADPR) synthesis were greater in CLL lymphocytes than in normal cells. Studies with a T-cell-depleted population of normal cells showed the same activity for poly(ADPR) synthesis that was demonstrated by the original population of normal cells. PHA stimulation produced an increase in poly(ADPR) synthesis in both the normal and CLL cells. The increase in poly(ADPR) synthesis in normal cells was coincident with the increase in DNA synthesis. The increase in poly(ADPR) synthesis in the CLL cells was dissociated from the delayed and diminished increase in DNA synthesis. Thus, CLL cells have higher than normal initial levels of poly(ADPR) synthesis. Poly(ADPR) synthesis is dissociated from DNA synthesis in CLL cells whereas it varies directly with DNA synthesis in normal lymphocytes.

Successful transplantation of the thymus in Nezelof's syndrome

A 6-month-old girl with congenital thymic dysplasia or Nezelof's syndrome (lack of T cell function and normal levels of immunoglobulins) was given a transplant of a human thymus gland from a 14-week-old fetus and is surviving 36 months after transplant. Her clinical condition is the principal index of the success of the transplant since most in vitro and in vivo data indicate a full immunologic restoration has not been achieved. However, the number of E-rosettes in the peripheral blood has increased, the number of surface immunoglobulin-bearing cells has decreased, but there is little improvement in mitogen responsitivity. Immunoglobulin levels have increased with age, but there is no demonstrable specific antibody activity. Nevertheless, she remains free of infection, living in an unprotected environment.

Humoral immunostimulation. VIII. Increased incorporation of phosphate and turnover of phosphatidylinositol in cells treated with antibody

Uptake of phosphate (32P) in L cells was modulated by reaction with anti-L cell antibody. A biphasic response was noted with high, cytotoxic concentrations inhibiting 32P uptake and low, cytostimulatory concentrations stimulating 32P uptake. Stimulation of 32P uptake was dependent upon multivalent binding as immune IgG and F(ab')2 were effective, but univalent Fab' was ineffective in enhancing 32P uptake into cells. Antibody stimulation of 32P uptake appeared to be an energy independent process and to take place by activation of 32P membrane transport with an increased Vmax (19.3 pmoles/min to 25.3 pmoles/min), but the same Km (0.22 mM). Isolation and measurement of cellular (primarily membrane) phospholipids demonstrated a dramatic increase of (2-fold) specific radioactivity in phosphatidylinositol. Early turnover of phosphatidylinositol may be an important signal for tumor cells to grow at an enhanced rate when exposed to cytostimulatory concentrations of antibody.

Humoral immunostimulation. VII. Sialic acid masks antigenic sites on an antibody-selected bariant cell line

Variant cell lines (LC1, LC2) obtained by growth of mouse L cells (L) in cytostimulatory and cytotoxic doses, respectively, of rabbit anti-L cell antiserum AL) were found previously to be altered in many ways relative to the parent cell line. A major change was the reduction of those surface membrane antigens that AL recognizes. These cell variants have now been found to have increased membrane sialic acid relative to L. Treatment of intact variant cells with neuraminidase (50 units/ml, 37 degrees C, 1 hr) greatly restored the susceptibility of LC1 to lysis with AL. In the presence of 1/100 dilution of AL and 5% complement the viability indices (1.00 = no cell kill) of untreated and neuraminidase-treated cells were respectively: L 0.10 and 0.03 and LC1 0.91 and 0.40. Neuraminidase-treated LC2 cells retained their resistance to AL. Parallel studies with 125I-ALIgG showed increased binding to neuraminidase-treated LC1 relative to native LC1. These findings suggest that the altered membrane sialic acid content affects the immunologic behavior of this cell variant by masking the original cell surface antibody-binding sites. This represents a possible mechanism for tumors to escape immunologic control.

Humoral immunostimulation. VI. Increased calcium uptake by cells treated with antibody and complement

When L cells were treated with anti-L cell antibody in medium depleted of complement, rapid increases in calcium uptake were obtained over a wide range of antiserum concentrations. Concomitant cell growth and viability studies demonstrated that stimulation of cell growth occurred at higher dilutions of antiserum whereas cytotoxicity occurred at lower dilutions. The stimulatory and toxic effects of antibody on cell growth were potentiated by complement as was the enhancement in calcium uptake. Sera deficient in C1R, C2,4D, C4, C3-C9 did not increase the calcium uptake response to antibody whereas augmentation did occur with C6-deficient serum. A specific role for complement was further indicated by the ability of purified complement components to restore the response to complement in complement-deficient sera. C3 with C3-C9 deficient serum, but not C2, C5, and C6 with C3-C9 deficient serum restored augmentation effects. Taken together with the results of previous studies it is apparent that complement augments both calcium and nucleoside uptake and that the effect is primarily via the classical complement pathway through C3. Substrate saturation studies demonstrated that antibody activated the facilitated diffusion of calcium altering the Vmax but not the Km of transport whereas addition of complement altered both the Vmax and Km. These findings suggest that one of the early effects of enhancing antibody upon tumor cell metabolism in vitro is to stimulate uptake of calcium. In view of the suspected role of Ca++ in cell proliferation the increase in cell-associated calcium may be important in the subsequent proliferative response.

Humoral immunostimulation. V. Selection of variant cell lines

A permanent L-cell variant cell line (LC1) was isolated by the growth of the parent L-cell line (L) in the presence of a cytostimulatory dose (1:200) of rabbit anti-L-cell antiserum (AL) for 9 mo. LC1 differed from L in many aspects: (a) it was larger (1,533 mm3 vs. 1,284 mm3), (b) it grew faster (1.5- to 2-fold), (c) it grew in aggregated fashion, (d) its growth was no longer stimulated by AL, (e) it was almost completely resistant to high concentrations of AL in the presence of complement (C), (f) its original membrane antigens (immunogenic for AL) were redistributed in sparse and patchy clumps as noted by fluorescence microscopy, (g) it contained about 65% of the total original 125I-AL membrane-binding sites (1.4 X 10(7)/cell vs. 2.2 X 10(7)/cell), (h) its AL-binding sites displayed a lower average affinity constant (K = 0.9 X 10(5) M-1 vs. 2.8 X 10(5) M-1), (i) it contained a smaller proportion of high affinity (K greater than 10(6) M-1) binding sites (13% vs 21%), and (j) LC1 was fully immunogenic in that it was readily killed by homologous antiserum (ALC1) and C, whereas L was not similarly affected by ALC1 indicating that LC1 contained new membrane antigens not present on L. Another variant (LC2) was produced by growth of LC1 in a 10-fold higher dose (1:20) of AL (cytotoxic for L) for 1 mo. LC2 was even more resistant to AL in the presence of C, contained 0.84 X 10(7) AL-binding sites/cell with an average affinity constant of 1 X 10(5) M-1 (unchanged from LC1), and was less susceptible than LC1 to lysis in the presence of ALC1 and C. These findings confirm and extend our previous in vitro and in vivo observations dealing with the direct stimulation effects of antibody on tumor cell metabolism and suggest that immunostimulation may be a mechanism of tumor escape from immune control in vivo possibly by immunoselection and antigenic modulation as proposed by other investigators.

Humoral immunostimulation. III. Requirements for divalent antibody and cellular aggregation

The intracellular incorporation of radioactive nucleoside into mouse L cells was stimulated by rabbit anti-L cell IgG antibody and by its divalent pepsin F(ab')2 fragment but not by univalent pepsin Fab' or papain Fab fragments. Divalent antibody also caused the cells to grow in an aggregated pattern and undergo capping, but univalent antibody did not. Prevention of aggregation of antibody-treated cells by growth in agar abrogated immunostimulation. Univalent antibody fragments partially blocked stimulation of cells by divalent antibody and binding of 125I-labeled divalent antibody to cells. These results suggest that immunostimulation of cell growth is dependent upon divalent antibody and that aggregation of cells is an associated event.

Alteration of L cell growth by antibody-stimulated incorporation of radioactive nucleosides

Radioactive nucleoside incorporation into mouse L cells was stimulated by exposure of the cells to rabbit anti-L cell antibody. Use of nucleosides of high specific radioactivity permitted a selective reduction of replication of antibody-treated cells as compared to control cells. The mechanism most likely involves radioactive damage of nuclear contents and DNA.

Humoral immunostimulation. IV. Role of complement

When L cells were treated with anti-L-cell antibody in medium containing heat-inactivated fetal calf serum, nucleoside uptake and cell growth were stimulated. The response was markedly increased when fresh, unheated sera from calves, guinea pigs, humans, mice, or rabbits were also present. The factors in unheated serum responsible for the enhancement of immunostimulation were studied. Using low concentrations of sera deficient in various complement (C) components and low concentrations of antibody no augmentation of immunostimulation was seen with Clr-deficient human serum, C2-deficient human serum, C2,4-deficient human serum, C4-deficient guinea pig serum, C3-C9-depleted guinea pig serum (by administration of cobra venom factor to animals), but stimulation was observed with C5-deficient human serum, C5-deficient mouse serum, and C6-deficient rabbit serum. When the concentration of anti-serum was raised, however, augmentation was observed with C4-deficient guinea pig serum. Thus, at low concentrations of antiserum enhancement appeared to occur through the classical C pathway, whereas at high concentrations of antibody either the classical or alternate C pathways appeared to be involved. Stimulation was specifically restored by purified C2 in C2-deficient serum and by C3 in C3-C9-deficient serum. Under the usual reaction conditions consumption of guinea pig C component C4 could be demonstrated which provided direct evidence for activation of the classical C pathway under conditions leading to immunostimulation. By immunofluorescence, cells treated with antibody and normal human serum had human C3 deposited at the cell surface. Taken together these observations suggest that C activated through C3 by either the classical or alternate pathways has the potential to enhance nucleoside incorporation into DNA and cell growth of cells exposed to limiting amounts of antibody. Although the mechanism of stimulation is unknown, it is likely to involve a direct effect of C3 at the level of the cell membrane.

Humoral immunostimulation. IV. Role of complement

When L cells were treated with anti-L-cell antibody in medium containing heat-inactivated fetal calf serum, nucleoside uptake and cell growth were stimulated. The response was markedly increased when fresh, unheated sera from calves, guinea pigs, humans, mice, or rabbits were also present. The factors in unheated serum responsible for the enhancement of immunostimulation were studied. Using low concentrations of sera deficient in various complement (C) components and low concentrations of antibody no augmentation of immunostimulation was seen with Clr-deficient human serum, C2-deficient human serum, C2,4-deficient human serum, C4-deficient guinea pig serum, C3-C9-depleted guinea pig serum (by administration of cobra venom factor to animals), but stimulation was observed with C5-deficient human serum, C5-deficient mouse serum, and C6-deficient rabbit serum. When the concentration of anti-serum was raised, however, augmentation was observed with C4-deficient guinea pig serum. Thus, at low concentrations of antiserum enhancement appeared to occur through the classical C pathway, whereas at high concentrations of antibody either the classical or alternate C pathways appeared to be involved. Stimulation was specifically restored by purified C2 in C2-deficient serum and by C3 in C3-C9-deficient serum. Under the usual reaction conditions consumption of guinea pig C component C4 could be demonstrated which provided direct evidence for activation of the classical C pathway under conditions leading to immunostimulation. By immunofluorescence, cells treated with antibody and normal human serum had human C3 deposited at the cell surface. Taken together these observations suggest that C activated through C3 by either the classical or alternate pathways has the potential to enhance nucleoside incorporation into DNA and cell growth of cells exposed to limiting amounts of antibody. Although the mechanism of stimulation is unknown, it is likely to involve a direct effect of C3 at the level of the cell membrane.

Humoral immunostimulation. I. Increased uptake of (125I)iododeoxyuridine and (3H)thymidine into TNP-cells treated with anti-TNP antibody

Interaction of microgram quantities of highly purified rabbit anti-TNP antibodies with TNP-substituted HeLa, HEp-2, and L cells caused an intense stimulation of radioactive nucleoside ([(125)I]UdR and [(3)H]TdR) uptake which was maximal 24-72 h after exposure of cells to antibody. The stimulation of nucleoside uptake and presumaly DNA synthesis was shown to be immuno logically mediated because unsubstituted cells were not stimulated by anti-TNP antibody, normal rabbit gamma globulin did not stimulate TNP-cells, and a hapten inhibitor, epsilon-DNP-lysine, prevented the stimulation of TNP-cells by anti-TNP antibody. These findings demonstrate that interaction of antibody with cell surface antigen can alter cell membrane transport, and possibly can enhance cell growth.

Stimulation of cells by antibody

Tumor cell lines exposed to immunoglobulins specific for cell surface antigens developed increased cellular incorporation of [(125)I]iododeoxyuridine and [(3)H]thymidine (up to 200-fold increases over cells treated with normal rabbit immunoglobulins). Antibody-stimulated cells multiplied more rapidly and lived longer than control cells in tissue culture. These observations were made both with cells substituted with 2,4,6-trinitrophenol and purified antibody against 2,4,6-trinitrophenol, and with several cell lines and their respective whole-cell antibodies. Antibodies that were stimulatory at low concentrations were cytotoxic at high concentrations. These observations may have significance in regard to enhancing effects of antibodies on tumor cell growth in vivo.