Immune response to immunization via the anterior chamber of the eye. I. F. lymphocyte-induced immune deviation.

The immunizing abilities of alloantigens placed within the anterior chamber of the eye have been studied in inbred rats. Although intracameral inoculation of F1 hybrid lymphocytes into parental strain recipients elicited both cell- and antibody-mediated immunity, a delimited interval was identified postinoculation during which the systemic cell-mediated immune response was suppressed as indicated by prolonged acceptance of orthotopic skin allografts. The prompt appearance of hemagglutinating antibodies in the serum of immunized rats followed a time course which coincided with the suppression of cell-mediated immunity and suggested that the two events are casually related. Since exposure to allogeneic antigens on lymphoid cells via the anterior chamber elicits a transient suppression in cell-mediated immunity, where humoral immunity is preserved, the phenomenon resembles immune deviation.     

Transplantation immunology of the anterior chamber of the eye. I. An intra-ocular graft-vs-host reaction (immunogenic anterior uveitis).

A graft-vs-host reaction (GVHR) expressed as an anterior uveitis was elicited within the anterior chambers of the eyes of F1 hybrid rats by the inoculation of suspensions of allogeneic, parental lymph node cells. This response resembled local GVHRs induced in other sites, except for the failure of refractoriness to appear following resolution of the acute phase. Because lymphoid cells within the anterior chamber have been shown to leave and make an impact on the systemic immunologic apparatus of the recipient, rather than remain isolated within the eye, it was suggested that the vascular route by which these cells disseminate is an important determinant of whether refractoriness will ensue from a local GVHR.     

Induction of anterior chamber-associated immune deviation (ACAID) by allogeneic intraocular tumors does not require splenic metastases

Anterior chamber-associated immune deviation (ACAID), induced by intracameral injection of allogeneic tumor cells, is expressed in three distinct ways: 1) progressive growth of intraocular tumors, 2) specific suppression of systemic allograft immunity, and 3) transient growth of allogeneic tumors injected subcutaneously. Induction of ACAID requires that alloantigen presentation occur via the anterior chamber; injection by other routes failed to elicit this phenomenon. Antigenic material must remain in the anatomically intact eye for at least 10 days; removal of the injected dye before this time prevented the establishment of ACAID. The similar temporal requirement for an anatomically intact spleen confirms the validity of the concept of a camero-splenic axis for processing of intracamerally injected alloantigens. Deployment of an alternate model of ACAID, using LP/J mice injected intracamerally with B16F10 melanoma, showed the antigen-specific inductive signal for ACAID (transmitted via the camero-splenic axis) was not in the form of viable alloantigen-bearing tumor cells that metastasize to the spleen. B16F10 melanoma cells were never found in the spleens or any other extraocular sites after intracameral injection, despite the fact these mice manifested ACAID and harbored enormous ocular tumors. The data emphasize that intraocular processing of antigens is a unique and dynamic phenomenon with significant, systemic immunologic consequences.     

Ocular immune responses. II. Priming of A/J mice in the vitreous induces either enhancement of or suppression of subsequent hapten-specific DTH responses

We previously showed that the "immunologic privilege" of the anterior chamber results not from afferent blockade, but rather from induction of hapten-specific suppressor T cells that appear after anterior chamber priming with antigen. These suppressor T cells induced by anterior chamber priming differ from those induced by i.v. priming in their ability to block the efferent as well as the afferent limb of the immune response and in their lack of idiotypic surface receptors detected by rabbit anti-idiotypic antibody. We now report that intravitreal priming with haptenated syngeneic spleen cells does not result in generation of suppressor cells, but rather, can in some instances result in an enhanced systemic immunoreactivity to the priming hapten. If soluble antigenic preparations are used, however, intravitreal priming results in the generation of the suppressor T cells, which suppress subsequent DTH and CTL responses to the immunizing hapten. The suppressor cell generation after intravitreal priming is a cyclophosphamide-sensitive process. These results demonstrate that soluble products are processed differently in ocular compartments compared with cell surface coupled ligands, and further demonstrate that the generation of hapten-specific suppressor T cells is dependent, at least in part, on the form and on the specific compartment of the eye that is inoculated.     

Immune response to immunization via the anterior chamber of the eye. II. An analysis of F1 lymphocyte-induced immune deviation

Exposure to alloantigen via the anterior chamber of the eye elicits a transient suppression of cellular immunity, whereas humoral immunity is preserved--i.e. F1 LI-ID. The majority of lymphoid cells inoculated into the anterior chamber are retained within the posterior segment of the eye. The latter serves as a depot of alloantigen, allowing the chronic egress of small numbers of cells into the vascular tree. The persistence of this antigen depot is essential to the development of F1 LI-ID. Since there is a preferential distribution of cells that migrate from the eye to the spleen, the functional integrity of the latter is also necessary to elicit F1 LI-ID. It is concluded that an anatomically intact spleen, i.v. presentation of antigen, and persistence of antigen within the eye are all important to the elicitation of this phenomenon.     

Intracamerally induced concomitant immunity: mice harboring progressively growing intraocular tumors are immune to spontaneous metastases and secondary tumor challenge

Intracameral inoculation of allogeneic P815 mastocytoma cells (DBA/2) into BALB/c mice resulted in progressively growing intraocular tumors. Intraocular tumor cells disseminated rapidly to the spleen and cervical lymph nodes, yet extraocular nests of tumor cells never developed into fulminant tumors. Further experiments showed that tumor cells were continuously seeded from the primary intraocular tumor and were rapidly cleared from extraocular sites. Hosts harboring intraocular P815 mastocytomas rejected tumorigenic doses of P815 cells inoculated subcutaneously or even into the contralateral anterior chamber. This systemic tumor immunity was found to be radiosensitive and T cell dependent. Spleen cells from animals with progressively growing intraocular tumors protected recipient mice challenged with intracamerally inoculated tumor cells and thus suggests that a cell-mediated mechanism is the underlying basis for this form of tumor immunity. The data indicate that mice harboring progressively growing intraocular tumors develop a potent state of "concomitant immunity," that prevents the development of metastases, yet is ineffective in controlling the primary tumor.     

Estrogen attenuates the exercise pressor reflex in female cats.

In humans, the pressor and muscle sympathetic nerve responses to static exercise are less in women than in men. The difference has been attributed to the effect of estrogen on the exercise pressor reflex. Estrogen receptors are abundant in areas of the dorsal horn receiving input from group III and IV muscle afferents, which comprise the sensory limb of the exercise pressor reflex arc. These findings prompted us to investigate the effect of estrogen on the spinal pathway of the exercise pressor reflex arc. Previously, we found that the threshold concentration of 17beta-estradiol needed to attenuate the exercise pressor reflex in male decerebrate cats was 10 microg/ml (Schmitt PM and Kaufman MP. J Appl Physiol 94: 1431-1436, 2003). The threshold concentration for female cats, however, is not known. Consequently, we applied 17beta-estradiol to a well covering the L6-S1 spinal cord in decerebrate female cats. The exercise pressor reflex was evoked by electrical stimulation of the L7 or S1 ventral root, a maneuver that caused the hindlimb muscles to contract statically. We found that the pressor response to contraction averaged 38 +/- 7 mmHg before the application of 17beta-estradiol (0.01 microg/ml) to the spinal cord, whereas it averaged only 23 +/- 4 mmHg 30 min after application (P < 0.05). Recovery of the pressor response to contraction was not obtained for 2 h after application of 17beta-estradiol. Application of 17beta-estradiol in a dose of 0.001 microg/ml had no effect on the exercise pressor reflex (n = 5). We conclude that the concentration of 17beta-estradiol required to attenuate the exercise pressor reflex is 1,000 times more dilute in female cats than that needed to attenuate this reflex in male cats.     

Depression of afferent arc of the in vivo cytotoxic T-cell immunity by bacterial lipopolysaccharides

The afferent arc of the in vivo cytotoxic T-cell immunity assessed by second set rejection of ascitic allogeneic tumors was shown to be depressed by bacterial lipopolysaccharide (LPS) that was administered simultaneously with or 1 day before injection of allogeneic spleen cells as stimulators. Two different LPSs from Escherichia coli O55 and Klebsiella O3 displayed similar activities whereas dextran sulfate, concanavalin A, or poly A:U was not effective. Stimulator activities of allogeneic cells was not directly modified by LPS. Any definite suppressor activity on afferent or efferent arc of the T-cell response was not demonstrable in mice receiving LPS and allogeneic cells. Further, the LPS effect for immune depression was not diminished by whole body X-ray irradiation to the recipient at 300 R, which ablated the B-cell reactivity to LPS for polyclonal activation, or by treatment of the recipient with carrageenan, a known toxic agent to macrophages. It was suggested from these results that LPS suppresses the cytotoxic T-cell immunity by modulating responder T cells to be temporarily refractory to the allogeneic stimulus rather than by activating suppressor cells such as radiation-sensitive lymphocytes and carrageenan-sensitive macrophages.     

Immunogenetic basis for immunologic privilege in the anterior chamber of the eye

DBA/2 mastocytoma (P815) cells are able to grow when inoculated into the anterior chamber of eyes of histoincompatible mice. Tumor growth is unrestrained in recipient mice differing from the DBA/2 strain at multiple minor H loci, but sharing the H-2 ^d haplotype; progressive tumor growth in these animals involves the entire eye, invades the orbit and kills the hosts by extension into the cranial vault. Alternatively, P815 cells grow initially but are unable to sustain continued growth in the anterior chambers of recipient mice differing from DBA/2 at the H-2 complex. Recipients differing from DBA/2 at either the K or D regions of H-2 develop anti-DBA/2 immunity that destroys the intraocular tumor within 20 days of inoculation. Severe inflammatory reactions in these eyes produce innocent bystander destruction of ocular tissue and produce blindness. Recipients differing from DBA/2 at both K and D regions of H-2 also mount vigorous anti-DBA/2 immunity that destroys the intraocular tumor. In these instances, the nonspecific component of the rejection reaction is minimal: when the tumor cells are destroyed, the eyes are restored to anatomic and functional integrity. These results indicate that immunologic privilege in the anterior chamber of the eye is afforded to allogeneic tissues to varing degrees depending upon allodisparity at H-2 loci encoding class I MHC products. The results further imply that the precision of the alloimmune response may be under the control of these same MHC products.     

Cell-mediated immunity to male-strain histocompatibility alloantigens detected after natural insemination and systemic immunization in the female mouse using the cell-mediated microcytotoxicity test

Female cell-mediated immunity to allogeneic spermatozoa after repeated natural insemination, in the absence of pregnancy, was compared with that after systemic challenge using the cell-mediated microcytotoxicity test to measure cytotoxic cell alloreactivity. After multiple (3-6) inseminations the majority of females (11 out of 13) showed a significant degree of lymphocytotoxicity to male-strain histocompatibility alloantigens in the para-aortic lymph nodes, and to a lesser extent in the spleens, while a single insemination was usually not sufficient to evoke a specific cytotoxic cell response. This differed from the low and highly variable degree of female sensitization after multiple systemic challenge with allogeneic spermatozoa via the intraperitoneal route. By contrast, a single systemic challenge via the footpad proved to be the most highly consistent and effective route for eliciting cell-mediated immunity to male-strain histocompatibility alloantigens in all 9 female mice. This alloreactivity appeared to be directed at alloantigens other than the male-specific H-Y antigen. These findings show that the precise route of immunization is a major factor in the development of female cell-mediated immune responsiveness to allogeneic spermatozoa.     

Characterization of the suppressor cell(s) responsible for anterior chamber-associated immune deviation (ACAID) induced in BALB/c mice by P815 cells

Anterior chamber-associated immune deviation (ACAID) is a complex set of immune responses induced by the inoculation of antigens into the anterior chamber of the eye. Histocompatibility antigens, tumor-specific antigens, reactive haptens, and viral antigens have been shown to induce this phenomenon, which comprises the following specific host responses: high titer humoral antibodies, primed cytotoxic T cells, but specifically, impaired skin graft rejection and delayed-type hypersensitivity (DTH). Using the model system of ACAID induced by inoculation of P815 mastocytoma cells into the anterior chambers of H-2-compatible, but minor H-incompatible, BALB/c mice, we demonstrate that the impaired capacity of these animals to develop and express DTH is due to the activation of suppressor T cells. Generation of these cells requires an intact spleen, is not inhibited by cyclophosphamide pretreatment, and is abrogated by systemic treatment of the host with anti-I-J monoclonal antibodies. This splenic suppressor cell(s) can transfer suppression of DTH adoptively to naive syngeneic mice. One suppressor cell is Thy-1.2, Lyt-2.2, and I-Jd positive. A minority of these cells (or a second population of suppressor cells) also expresses the L3T4 surface marker. Suppression is exerted on the efferent limb of DTH expression, although afferent suppression is not excluded. P815-induced ACAID suppressor cells resemble similar cells induced by haptenated spleen cells inoculated into the anterior chamber of the eye. We propose that induction of these suppressor cells, whose target of action is selective for T DTH cells, but not for other types of T cells, is responsible for the phenomenon of immune privilege in the anterior chamber of the eye.     

Protection of mice from herpes simplex virus-induced retinitis by in vitro-activated immune cells.

A form of acute retinal necrosis occurred in the contralateral eyes of susceptible mice 1 week after each received a uniocular injection of live herpes simplex virus type 1 (HSV-1) in the anterior chamber. Although these mice did not develop systemic delayed hypersensitivity to virus antigens, their sera contained virus-specific antibodies at the time contralateral retinitis occurred. These findings suggest that systemic immunity might not be able to protect against contralateral retinitis. To explore this possibility further, we examined lymph nodes and spleens of intraocularly infected mice to determine whether their lymphoid tissues contained primed HSV-1-specific cytotoxic T cells. Virus-specific cytotoxic T cells were readily identified in these mice. We wondered why successful immune priming did not confer protection against HSV-1 retinitis. We examined this issue by evaluating the capacity of in vitro-generated, HSV-1-specific effector T cells to prevent retinitis by infusing these cells by various routes and at various times into mice that received an intracameral injection of HSV-1. The results revealed that virus-specific effector cells could prevent contralateral retinitis if injected intravenously or into the anterior chamber of the contralateral eye at the same time that virus was injected into one eye. However, the effector cells failed to prevent retinitis if they were injected into the same eye that received HSV-1 or if their intravenous administration was delayed until 24 h after the HSV-1 injection into the eye. We concluded that immune T cells can protect against contralateral retinal necrosis caused by uniocular injection of HSV-1 into the anterior chamber but only if they are administered during the first 24 h after virus infection. We propose that a retinitis-inducing process is set in motion during this early time interval postinfection. Once the process has been initiated and established, it is no longer susceptible to immune intervention. It would appear that mice that are susceptible to contralateral retinitis fail to mobilize a protective response quickly enough to ward off the establishment of the retinitis-inducing process and its disastrous eventuality.     

Reflex responses to reductions in functioning renal mass

Both acute unilateral nephrectomy (AUN) and unilateral ureteral obstruction (UUO) result in an acute increase in cation excretion from the contralateral kidney. AUN results in reflex changes in systemic hemodynamics owing to an acute and transient increase in arterial pressure that activates carotid sinus baroreceptors and constitutes an afferent limb in the reflex; hemodynamic adjustments and increased cation excretion result. The reflex involves participation of the endogenous opioid system, with receptors located primarily in the central nervous system, and requires intact pituitary function because both hypophysectomy and pretreatment with large doses of dexamethasone prevent the postnephrectomy natriuresis. The natriuresis is closely correlated with an increase in the plasma concentration of the NH2-terminal fragment of the pituitary peptide precursor molecule proopiomelanocortin, which suggests that such a peptide could participate directly or indirectly in the postnephrectomy natriuresis. Surgical denervation of either the ipsilateral or the contralateral kidney markedly alters the response to AUN, which prevents the natriuresis and blunts the kaliuresis, and indicates a role for renal neural reflexes. Renorenal reflex pathways also mediate the response of the contralateral kidney to UUO, because denervation of either the ipsilateral (obstructed) or the contralateral kidney abolishes both the natriuresis and kaliuresis usually seen after UUO. This reflex also involves the endogenous opioid system, for it does not occur in rats receiving an i.v. infusion of the opiate receptor antagonist naloxone.     

Postnatal development of node-paranode regions in two hind limb nerves of the cat

Node-paranode regions of large myelinated axons from the nerves to the lateral gastrocnemius muscle (ankle extensor) and the anterior tibial muscle (ankle flexor) were studied in the cat during postnatal development and examined with regard to the occurrence of paranodal Schwann cell Marchi-positive bodies and mitochondria. It was found, in newborn kittens with respect to both parameters, that paranodes of flexor nerve fibers, being part of the functionally more developed ankle flexor reflex arc [cf. Mellström, A. (1971). Acta Physiol. Scand., 82, 477–489], appeared more mature than did those of extensor nerve fibers, which are part of the less developed ankle extensor reflex arc. It is concluded that the maturation of large feline hind limb muscle nerve fibers runs through a “nodalization” process similar to that described earlier for feline lumbar spinal root fibers [cf. Berthold, C.-H. (1973). Neurobiology, 3, 339–352] and that this normally occurring, rather striking remodeling of the node-paranode regions is likely to be functionally significant.     

Ocular immune responses. I. Priming of A/J mice in the anterior chamber with azobenzenearsonate-derivatized cells induces second-order-like suppressor T cells

We studied the cellular immune responses to ocular anterior chamber (AC) priming of mice. A/J mice primed subcutaneously with azobenzenearsonate-coupled spleen cells (ABA-SC) manifested delayed-type hypersensitivity (DTH) in the form of footpad swelling when challenged 5 days later with the diazonium salt of ABA. Mice inoculated with ABA-SC in the anterior chamber at the time of subcutaneous priming, however, were tolerant to ABA. Subconjunctival inoculation with ABA-SC did not tolerize; rather it primed for DTH. Antibodies against ABA were not detectable in significant amounts in mice made tolerant by AC inoculation. The AC-induced tolerance was shown to result from hapten-specific T cell-mediated suppression. Suppressor T cells (Ts) arising from AC priming suppressed the efferent limb of the immune response and did not bear detectable cross-reactive idiotype (CRI) surface receptors. In these phenotypic and functional respects, AC-induced Ts differed from first-order Ts (Ts1) that result from i.v. priming. The results are discussed with respect to immune privilege and the anterior chamber of the eye.     

Maintenance of immune tolerance depends on normal tissue homeostasis

Ags expressed at immune privileged sites and other peripheral tissues are able to induce T cell tolerance. In this study, we analyzed whether tolerance toward an intraocular tumor expressing a highly immunogenic CTL epitope is maintained, broken, or reverted into immunity in the event the anatomical integrity of the eye is lost. Inoculation of tumor cells into the anterior chamber of the eye of naive B6 mice leads to progressive intraocular tumor growth, an abortive form of CTL activation in the tumor-draining submandibular lymph node, and systemic tolerance as evidenced by the inability of these mice to reject an otherwise benign tumor cell inoculum. Loss of anatomical integrity of the eye as a consequence of phthisis resulted in loss of systemic tolerance and the emergence of effective antitumor immunity against an otherwise lethal tumor challenge. Phthisis was accompanied by dendritic cell maturation and preceded the induction of systemic tumor-specific CTL immunity. Our data show that normal tissue homeostasis and anatomical integrity is required for the maintenance of ocular tolerance and prevention of CTL-mediated immunity. These data also indicate that tissue injury in the absence of viral or microbial infection can act as a switch for the induction of CTL immunity.     

Cephalic influences on a defensive behaviour in the dogbane tiger moth, Cycnia tenera

ABSTRACT. The dogbane tiger moth ( Cycnia tenera Hübner; Arctiidae) responds to ultrasonic, artificial bat echolocation signals by emitting stereotyped trains of high-frequency, rapidly repeated clicks. By comparing this response in intact and headless moths, the role of protocerebral auditory inter-neurones suggested by other studies was examined. Individual moths were tested intact and decapitated, and their response differences analysed. Response latency and threshold (dB) did not alter with the removal of the head but response duration and responsiveness to stimulus trains were significantly reduced in headless moths. These data are interpreted as suggesting the existence of a reflex arc connecting the moth's tympanic organ (ear) with its sound-producing structure (tymbal), and as providing preliminary evidence that the role of higher-order interneurones is primarily that of response reinforcement.     

Regulation of wrist stiffness by the stretch reflex

In restoring the angular position after a displacement, the role of the muscle stretch reflex was investigated by comparing the restored angular torques and angular positions in the wrist under ischaemic and non-ischaemic conditions in normal human subjects. The wrist compliance (COM), defined as the dynamic relation between the angular position and the angular torque of the joint, was calculated to quantify the changes in the restoration of a displacement after abolishing the stretch reflex by ischaemia. The elasticity from the COM-function was found to be single most important factor controlled by the stretch reflex. The elasticity that equals the static stiffness of the system increased by more than 100%, from 0.21 Nm degree-1 with abolished reflex to 0.45 Nm degree-1 with intact reflex. Our results have shown that the stretch reflex assists in the rapid return of the limb to its original position after a mechanical displacement. When the reflex was blocked by ischaemia, the perturbation displaced the limb further away from the initial position.     

Different fusimotor reflexes from the ipsi- and contralateral hind limbs of the cat assessed in the same primary muscle spindle afferents

Experiments were performed in forty-five cats anaesthetized with alpha-chloralose. The aim of the study was to investigate a sample of primary muscle spindle afferents from triceps muscle with respect to their fusimotor reflex control from ipsi- as well as contralateral hind limb. Primary muscle spindle afferents of the triceps surae muscle were recorded from the mean rate of firing and the modulation of the afferent response to sinusoidal stretching of the triceps surae muscle was determined. Test measurements were made during tonic stretch of the ipsilateral PBSt, contralateral PBSt, contralateral triceps muscle or during extension of the intact contralateral hind limb. Control measurements were made with ipsi- and contralateral PBSt as well as contralateral triceps muscles relaxed and with contralateral hind limb in resting position. The occurrence and types of fusimotor effects were assessed by comparing test to control responses. The main finding of the present investigation was the great variability in type and size of the fusimotor effects evoked by different ipsi- and contralateral reflex stimuli. Both ipsi- and contralateral stimulations gave rise to predominantly dynamic, predominantly static or mixed static and dynamic fusimotor reflexes. In the same preparation, a given reflex stimulus often caused different reflex responses in different triceps surae primary spindle afferents. In the same afferent unit, different reflex stimuli usually produced fusimotor effects which differed from each other in type and/or size. In general, contralateral whole limb extension and stretch of contralateral PBSt muscles were more potent as reflex stimuli than stretch of the ipsilateral PBSt muscle. Stretch of the contralateral triceps surae muscle was, but for a few afferent units, ineffective as reflexogenic stimulus. It is concluded that the individualized receptive profiles of the primary muscle spindle afferents, which have been postulated in earlier investigations where the effects of different stimuli have been investigated on different cell populations, still seems to hold good when the stimuli are tested on the same units. The individuality of the receptive profiles of gamma-motoneurones is discussed in relation to different motor control hypotheses.