Pathogenetic mechanisms in immune polioencephalomyelitis: induction of disease in immunosuppressed mice.

Immune polioencephalomyelitis (IPE) was induced by the i.p. injection of x-irradiated (10, 000 R) syngeneic line Ib malignant lymphocytes into C58 mice that were 7 or more months old and in young mice immunosuppressed by x-ray or drugs. The occurrence of IPE in young immunosuppressed C58 mice was systematically analyzed. When mice less than 2 weeks old were x-irradiated with 600 R, IPE could not be induced. The incidence in 1-month-old mice was approximately 50% and increased progressively with the age except for a drop in incidence at 3 months. An analysis of the dose effects of x-irradiation on the occurrence of IPE in mice of different ages revealed a marked increase in the incidence in 3- and 5-month-old mice beginning at dose levels of 450 R and 300 R, respectively. Considered together, these data indicated that two subpopulations of immunocytes differing in x-ray sensitivity interacted to protect mice from IPE. It appears that under natural conditions an x-ray sensitive cell population, possibly having suppressor function, decreased with age and made mice susceptible ot induction of IPE. Five-month-old mice were immunosuppressed with an LD10 of cyclophosphamide, prednisolone, or methotrexate to determine whether mice immunosuppressed with drugs also were susceptible to the induction of IPE. The incidence was 89%, 13%, and 5%, respectively. The mouse strain specificity of IPE induction also was studied. In 6- to 8-month-old mice suppressed with 600 R, IPE could not be induced in non-H-2k strains: BALB, C57BL/6, NZB. Of the H-2K strains tested (CBA/J, C3H/He, AKR/J, C58), the disease could be induced only in the C58 and AKR/J strains. Histopathologic studies showed that CNS lesions in immunosuppressed C58 and AKR/J mice did not differ significantly from those in old C58 mice with IPE. Taken together, the results of these studies indicate that IPE can be used as a model for analyzing age-dependent diseases of suspected immunopathologic etiology.     

Immune mechanisms in leukemia: protective capacity of the major lymphoid cell compartments.

The capacity of immune spleen, lymph node, peritoneal, bone marrow, and thymic cells to protect C58/wm mice from syngeneic transplanted line Ib leukemia was quantified. Cells harvested 14 to 15 days after primary immunization were used for adoptive protection tests. Regression curves were computer analyzed and log10, PD50 values compared. For immune spleen, lymph node, peritoneal, bone marrow, and thymic cells the PD50 values were 4.53, 5.92, 4.88, 5.51, and 5.59, respectively. When immune spleen cells were treated with anti-Thy 1.2 serum the PD50 value was increased from 4.73 to 6.09, i.e., protection was reduced greater than or equal to 95%. Similar treatment of immune thymic cells reduced protection below measureable values. Anti-B cell sera (anti-IgM and anti-Ly 4.2) did not reduce the protective effect of immune spleen or marrow cells. These results indicate that a major protective cell population in each of these compartments was theta-positive. Experiments were carried out to characterize the cortisone (CS) and x-ray sensitivity of immune spleen, thymic, and marrow cells .When donor mice were treated with 12.5 mg of cortisone acetate/day for 2 days before lymphoid cells were harvested, the orotective effects of immune spleen cells, but not immune thymic or marrow cells, was reduced. When immune spleen cells were x-irrated in vitro, their protective effect was reduced by 350 R and abolished by 1000 R. When mice received whole boyd x-irradiation 24 hr before immune spleen cells were transferred their protective effect was reduced by 1000 R but only slightly lowered by 350 R. The possible significance of the multicompartmental nature of immunity to leukemia was discussed.     

Studies on the transfer of protective immunity with lymphoid cells from mice immune to malaria sporozoites.

In an effort to understand the mechanisms involved in the protective immunity to malarial sporozoites, an A/J mouse/Plasmodium berghei model was studied. Protective immunity could consistently be adoptively transferred only by using sublethal irradiation of recipients (500 R); a spleen equivalent (100 X 10(6))of donor cells from immune syngeneic mice; and a small booster immunization (1 X 10(4)) of recipients with irradiation-attenuated sporozoites. Recipient animals treated in this manner were protected from lethal challenge with 1 X 10(4) nonattenuated sporozoites. Immune and nonimmune serum and spleen cells from nonimmune animals did not protect recipient mice. Fewer immune spleen cells (50 X 10(6)) protected some recipients. In vitro treatment of immune spleen cells with anti-theta sera and complement abolished their ability to transfer protection. This preliminary study suggests that protective sporozoite immunity can be transferred with cells, and that it is T cell dependent.     

Photoinhibition of photosynthesis. An evaluation of damaging and protective mechanisms

Inhibition of photosynthesis by excess excitation energy is initiated in the reaction center of photosystem II. The primary site of photoinhibition in the reaction center (components of primary charge separation or secondary electron acceptor Q_B) is still disputed. Photoinhibition is characterized by quenching of variable chlorophyll flurescence (F_v), resulting from increased thermal dissipation of excitation energy. Varying responses of initial fluorescence (F₀), however, seem to indicate involvement of different mechanisms. As far as photoinhibition is reversible within minutes to hours, it can be viewed as a controlled protective mechanism that serves to dissipate excessive energy, Supposedly, another dissipative mechanism, distinguished by its faster kinetics (response within seconds), is related to the energy-dependent fluorescence quenching.     

Purified mouse mammary tumor and lymphoid cells in immune assays

Summary Tumor and lymphoid cell components from primary mammary adenocarcinomas of C3H/He mice were isolated simultaneously by velocity gradients. Viable tumor cells were obtained in sufficient numbers to test their in vivo and in vitro growth. Isolated tumor cells grew in 97% of inoculated syngeneic animals. In six assays with different tumors the effects of tumor-associated lymphoid cells (TAL) on in vivo tumor growth varied, enhancing in three and delaying in two experiments. Isolated tumor cells from animals with enhancing TAL grew faster in nonirradiated mice, whereas tumor cells from animals with inhibitory TAL grew better in irradiated animals. Isolated tumor cells also proliferated in cell culture, where they averaged 35% primary plating efficiency. Separated tumor cells were used in short-term ⁵¹Cr-release assays with TAL, tumor-bearer lymph node and spleen effectors. Cytotoxicity was detected in only five of 25 assays. In no case was there killing by lymphocyte populations from normal animals. In the present report we describe a technique for the isolation of viable tumor and lymphoid cells from murine adenocarcinomas that allows study of interactions between these populations from the original tumor-bearing host.Postdoctoral fellow of the Fogarty International Foundation. Present address: Department of Surgery, Harvard Medical School and Brigham & Women's Hospital, Boston, MA 02215, USA     

Inhibition of in vitro immune response by extracts from long-term cultured lymphoid cells.

Ultrasonic cell extracts prepared from long term calf lymphoid cell cultures (LTE) inhibit the primary in vitro response to sheep red blood cells, either of young calf lymphocytes or of mouse spleen cells. LTE do not affect lymphocyte stimulation by Con A or LPS. The activity disappears after treating LTE with protease. The molecular weight of the active factors estimated by Diaflo ultrafiltration is 10,000 to 15,000 D.     

Proteinase-activated receptor-2 exerts protective and pathogenic cell type-specific effects in Alzheimer's disease

The proteinase-activated receptors (PARs) are a novel family of G protein-coupled receptors, and their effects in neurodegenerative diseases remain uncertain. Alzheimer's disease (AD) is a neurodegenerative disorder defined by misfolded protein accumulation with concurrent neuroinflammation and neuronal death. We report suppression of proteinase-activated receptor-2 (PAR2) expression in neurons of brains from AD patients, whereas PAR2 expression was increased in proximate glial cells, together with up-regulation of proinflammatory cytokines and chemokines and reduced IL-4 expression (p < 0.05). Glial PAR2 activation increased expression of formyl peptide receptor-2 (p < 0.01), a cognate receptor for a fibrillar 42-aa form of beta-amyloid (Abeta(1-42)), enhanced microglia-mediated proinflammatory responses, and suppressed astrocytic IL-4 expression, resulting in neuronal death (p < 0.05). Conversely, neuronal PAR2 activation protected human neurons against the toxic effects of Abeta(1-42) (p < 0.05), a key component of AD neuropathogenesis. Amyloid precursor protein-transgenic mice, displayed glial fibrillary acidic protein and IL-4 induction (p < 0.05) in the absence of proinflammatory gene up-regulation and neuronal injury, whereas PAR2 was up-regulated at this early stage of disease progression. PAR2-deficient mice, after hippocampal Abeta(1-42) implantation, exhibited enhanced IL-4 induction and less neuroinflammation (p < 0.05), together with improved neurobehavioral outcomes (p < 0.05). Thus, PAR2 exerted protective properties in neurons, but its activation in glia was pathogenic with secretion of neurotoxic factors and suppression of astrocytic anti-inflammatory mechanisms contributing to Abeta(1-42)-mediated neurodegeneration.