Phylogeny of immune recognition: processing and presentation of structurally defined proteins in channel catfish immune responses

This work was undertaken to investigate whether or not antigen processing and presentation are important in channel catfish in vitro secondary immune responses elicited with structurally defined proteins, namely, pigeon heart cytochrome C (pCytC), hen egg lysozyme, and horse myoglobin. The use of in vitro antigen-pulsed and fixed B cells or monocytes as antigen presenting cells (APC) resulted in autologous peripheral blood leukocytes (PBL) responding with vigorous proliferation and antibody production in vitro. In addition, several long-term catfish monocyte lines have been found to function as efficient APC with autologous but not allogeneic responders. Subsequent separation of the responding PBL into sIg- (T-cell-enriched) and B (sIg+) cells subsets showed that both underwent proliferative responses to antigen-pulsed and fixed APC. Moreover, allogeneic cells used as APC were found to induce only strong mixed leukocyte reactions without specific in vitro antibody production. Initial attempts at identifying the immunogenic region(s) of the protein antigens for catfish indicated there are two such regions for pCytC, namely, peptides 66-80 and 81-104.

Phylogeny of immune recognition: antigen processing/presentation in channel catfish immune responses to hemocyanins

Studies were conducted to address the role(s) of antigen (Ag) processing/presentation in channel catfish immune responses. Vigorous and specific secondary in vitro proliferative and antibody (Ab) responses were obtained to keyhole limpet and Limulus polyphemus hemocyanins with peripheral blood leukocytes (PBL) from catfish previously primed in vivo with Ag. In addition, such antigen-specific in vitro proliferative and Ab responses were efficiently elicited by antigen-pulsed and subsequently paraformaldehyde-fixed autologous PBL used as putative antigen-presenting cells (APC) but not by APC fixed prior to Ag pulsing. Treatment of these putative APC with lysosomotropic agents, protease inhibitors, or the ionophore monensin prior to or during pulsing with Ag significantly inhibited both in vitro responses. Furthermore, the use of radiolabeled protein indicated that both untreated and inhibitor-treated PBL but not erythrocytes take up Ag; however, only untreated PBL were able to degrade Ag. Immune restriction was indicated by the use of allogeneic PBL as APC in that only strong MLRs were generated with no detectable antibodies produced in vitro. Finally, the employment of isolated leukocyte subpopulations demonstrated that both catfish B (sIg+) lymphocytes and monocytes were efficient Ag presentors.

The immunoglobulin M heavy chain constant region gene of the channel catfish, Ictalurus punctatus: an unusual mRNA splice pattern produces the membrane form of the molecule

The immunoglobulin (IgM) heavy chain constant region gene of the channel catfish, Ictalurus punctatus, has been cloned and characterized. The gene contains four constant region domain-encoding exons (CH1 to CH4) expressed in the secreted form of the immunoglobulin, and two exons encoding the transmembrane (TM) domain utilized in the lymphocyte membrane receptor form of the immunoglobulin. The sequence of a cDNA clone encoding the 3' region of the message for the membrane receptor form of the mu chain indicates that the TM1 exon is spliced directly to the CH3 exon, and not into a site within the CH4 exon, as occurs in the mammals, a shark and an amphibian. This unusual pattern of splicing, which produces a membrane heavy chain that is characteristically smaller than the secreted heavy chain, may be common to all teleost fish.

Temperature-mediated processes in immunity: differential effects of low temperature on mouse T helper cell responses

A low culture temperature of 27 degrees C inhibited mouse primary in vitro anti-hapten plaque-forming cell responses to a thymus-dependent (TD) antigen (Ag) (trinitrophenyl-keyhole limpet hemocyanin, TNP-KLH). In contrast, the magnitudes of secondary responses to TNP-KLH or primary responses to a thymus-independent (TI) Ag (TNP-lipopolysaccharide (LPS)) were unaffected. The low-temperature-sensitive step in the primary TD response occurred relatively early and preceded interleukin 2 (IL-2) secretion. Furthermore, the low-temperature-induced suppression could be obviated (rescued) by recombinant IL-2 or IL-4, but not by IL-1. Thus, the low temperature appeared to inhibit the function of virgin Th cells by preferentially affecting T cell-derived interleukin synthesis/secretion and not other cellular activities. These results also imply fundamental differences between the activation requirements of memory and virgin Th cells.

Channel catfish as an unconventional model for immunological studies

The channel catfish, Ictalurus punctatus, is an economically important species which is readily available, acclimates well to the laboratory setting, and is amenable to considerable experimental manipulation. Although the channel catfish is still a relatively circumscribed species in terms of comprehensive physiologic and/or endocrinologic studies, our current understanding of the basic immunobiology and immunochemistry of the channel catfish is significantly further advanced than for any other teleost species. In this respect the channel catfish is not only proving useful in the general areas of comparative immunology but it is also showing considerable promise as a model system for definitive studies on problems which bridge the fields of immunology and endocrinology, i.e., understanding the effects of environmental temperature and stress on the immune system.

Differential effects of temperature and exogenous fatty acids on mitogen-induced proliferation in channel catfish T and B lymphocytes

1. Exogenously supplied, BSA complexed saturated and unsaturated fatty acids were compared for their effects on mitogen-induced DNA synthesis in channel catfish T and B lymphocytes. 2. At "permissive" in vitro temperatures (27 degrees C), high concentrations (greater than or equal to 240 microM) of all the fatty acids used were inhibitory. However, at lower concentrations (80-160 microM), differences were noted in the ability of some fatty acids to modulate mitogen responses. While palmitic acid (16:0) and linoleic acid (18:2) had little effect on LPS-induced B cell- or Con A-induced T cell proliferation, stearic acid (18:0) suppressed while oleic acid (18:1) enhanced T cell responses only. 3. Adding equimolar amounts of 18:0 and 18:1 obviated the effects of singularly added fatty acids on T cell mitogenesis. 4. 18:1 was used to successfully "rescue" approximately 60% of the Con A-induced T cell proliferation normally inhibited at "nonpermissive" in vitro temperatures (17 degrees C). 5. While B cells readily appear to desaturate 18:0 and synthesize unsaturated fatty acids, T cells accumulate comparatively large amounts of 18:0 in membrane associated phospholipids. 6. It is proposed that 18:1 enhances T cell responses at permissive high temperatures and rescues suppressed T cell responses at nonpermissive low temperatures by increasing membrane fluidity.

Unsaturated fatty acids inhibit IL-2 production in thymus-dependent antibody responses in vitro

Albumin-complexed unsaturated fatty acids such as oleic acid (18:1) exerted a dose-dependent inhibitory effect on in vitro primary anti-TNP plaque-forming cell (PFC) responses to trinitrophenyl keyhole limpet haemocyanin (TNP-KLH), but did not affect primary PFC responses to trinitrophenyl lipopolysaccharide (TNP-LPS). The addition of 150 microM 18:1 at the initiation of thymus-dependent (T-D) antibody cultures inhibited the subsequent PFC response by 85%, and removal of the fatty acid after 24 hr did not reverse its inhibitory effect. By contrast, delaying the addition of 18:1 until 3 or 4 days after culture initiation abrogated its inhibitory effects. T-D antibody cultures displayed maximum production of interleukin-2 (IL-2) on the third day after culture initiation and a 24-hr exposure to 18:1 resulted in a dose-dependent inhibition of IL-2 production. Lastly, the addition of exogenous IL-2 reversed the inhibition of PFC responses in cultures transiently exposed to 18:1. These findings suggest that unsaturated fatty acids inhibit in vitro T-D PFC responses by selectively interfering with early stages of the antibody response, particularly those events leading to IL-2 production by T-helper cells.

Amonabactin, a novel tryptophan- or phenylalanine-containing phenolate siderophore in Aeromonas hydrophila

Aeromonas hydrophila 495A2 excreted two forms of amonabactin, a new phenolate siderophore composed of 2,3-dihydroxybenzoic acid, lysine, glycine, and either tryptophan (amonabactin T) or phenylalanine (amonabactin P). Supplementing cultures with L-tryptophan (0.3 mM) caused exclusive synthesis of amonabactin T, whereas supplements of L-phenylalanine (0.3 to 30 mM) gave predominant production of amonabactin P. The two forms of amonabactin were separately purified by a combination of production and polyamide column chromatographic methods. Both forms were biologically active, stimulating growth in iron-deficient medium of an amonabactin-negative mutant. Of 43 additional siderophore-producing isolates of the Aeromonas species that were tested, 76% (19 of 25) of the A. hydrophila isolates were amonabactin positive, whereas only 19% (3 of 16) of the A. sobria isolates and all (3 of 3) of the A. caviae isolates produced amonabactin, suggesting a predominant synthesis of amonabactin in certain Aeromonas species.

Ligand binding by murine IgM antibodies: intramolecular heterogeneity exists in certain, but not all, cases

The ligand binding properties of eight hybridoma-derived murine anti-DNP IgM(kappa) antibodies were analysed by equilibrium dialysis. Four of these proteins exhibited the expected valances of approximately 10 and relatively low affinities (less than or equal to 2.2 x 10(5) M-1). The remaining four proteins exhibited valences of considerably less than 10 (less than or equal to 8) and relatively high affinities (greater than 10(6) M-1). When these proteins were subjected to two cycles of lyophilization, those of the former group were observed to still exhibit approximately 10 sites per molecule with homogeneous affinities similar to those of the respective untreated molecules. However, molecules in the latter group (valences of less than or equal to 8) were observed to exhibit only five to six binding sites subsequent to lyophilization with no changes in affinities. When the reductive subunits from each of the IgM(kappa) proteins were subjected to trypsinization, two different patterns were observed in terms of the yields of Fab mu fragments. Each of the proteins originally exhibiting approximately 10 binding sites yielded greater than 90% of the expected Fab mu fragments. In contrast each of the proteins exhibiting less than or equal to 8 binding sites yielded only approximately 50% of the expected Fab mu fragments. Collectively these results indicate the existence of at least two different forms of murine IgM molecules, those with approximately 10 homogeneous, relatively stable sites and those with only approx. five stable sites. It is suggested that these intramolecular functional differences may be attributable to intramolecular conformational differences.

Temperature-mediated processes in teleost immunity: homeoviscous adaptation by channel catfish peripheral blood cells

1. Channel catfish peripheral blood erythrocyte, thrombocyte, T cell and B cell membranes were assayed by fluorescence depolarization using the fluorescent probe 1,6-diphenyl-1,3,5 hexatriene (DPH) to determine the effects of in vivo temperature acclimation on membrane viscosity and the kinetics of homeoviscous adaptation. 2. Erythrocyte membranes did not undergo homeoviscous adaptation during the 8 week time period studied and were more rigid compared with those of the other cell types. 3. The kinetics of homeoviscous adaptation exhibited by membranes from T cells, B cells and thrombocytes differed: B cells required 1-3 weeks while T cells and thrombocytes each required 3-5 weeks. Membranes from T cells, B cells and thrombocytes from fish acclimated for relatively short times (less than or equal to 3 weeks) exhibited similar membrane fluidities. 4. T cells from channel catfish appeared not only to be sensitive to temperature but also to a factor(s) independent of temperature but correlated to long term in vivo acclimation, i.e. T cell membranes underwent additional decreases in membrane viscosity between 3 and 5 weeks. 5. In conclusion, it appears that low temperature-mediated immunosuppression of T cell functions in channel catfish is probably not due to an inherent non-adaptability or rigid nature of the T cell membranes.

Temperature mediated processes in teleost immunity: differential abilities of channel catfish T and B lymphocytes to cap membrane antigen

1. The effect of both in vivo acclimation temperature and in vitro assay temperatures on channel catfish T and B lymphocyte membrane antigen (mAg) capping were investigated to determine if capping might be the temperature sensitive step involved in the low temperature immunosuppression of channel catfish T cell responses. 2. Flow cytometry was used to monitor the kinetics of capping induced by a mouse monoclonal antibody (mAb 11G3) specific for a common antigenic determinant present on channel catfish T and B cells. Results indicated that the kinetics of mAg capping were dependent on in vitro assay and in vivo acclimation temperatures and the length of time of in vivo acclimation. 3. T cells from fish appropriately acclimated to 27 degrees C cap mAg more efficiently at low assay temperatures than do B cells. 4. Activation energies were 32 and 47 kcal/mol for B and T cells, respectively, from fish acclimated to 17 degrees C for 3 weeks, but were significantly lower (14 and 22 kcal/mol, respectively) after acclimation for 5 weeks. 5. In summary, it appears that after appropriate in vivo acclimation, channel catfish T cells are better able to cap mAg at low assay temperatures than are B cells. These results suggest that mAg capping is not the low temperature sensitive step involved in T cell immunosuppression in channel catfish.

Conformational changes in the DNA of hybridoma cells from pristane treated mice

The effects of pristane on the DNA of hybridoma cells propagated as ascitic tumors in pristane-primed BALB/c mice were determined using flow cytometric analyses. Hybridoma cells maintained in vitro or cell isolates from solid tumors which developed in unprimed mice injected with hybridoma cells exhibited similar propidium iodide (PI) staining characteristics. In contrast, PI stained cells isolated from ascites which developed in pristane-primed mice injected with the hybridoma cells displayed significant decreases in fluorescence intensity. Diphenylamine studies and analyses of pH 10 treated cells indicated that the actual DNA content of the hybridoma cells was not altered by exposure to pristane. Furthermore, the altered staining characteristics of the ascitic tumor cells were reversible in that the fluorescence intensity after serial in vitro passage of the ascites cells was similar to that of the parent cell line which had not been exposed to pristane. In addition, there was a direct correlation between the altered PI staining characteristics and the presence of cell-associated pristane as determined by gas-liquid chromatography analyses of cell extracts. Collectively these results suggest that pristane may have a direct effect on the DNA conformation of hybridoma cells which may in turn enhance their growth as ascitic tumors. The possible role of such an altered DNA conformation in hybridoma cells on the in vivo development of ascites is discussed.

Cortisol-induced hematologic and immunologic changes in channel catfish (Ictalurus punctatus)

1. Intravenous injections of physiologic doses of cortisol resulted in both hematologic and immunologic changes in channel catfish peripheral blood leucocytes. These changes mimicked those seen when catfish were acutely stressed by handling and transport. 2. Eighteen hours after the administration of cortisol, decreases in the number of circulating lymphocytes and concomitant increases in the number of circulating neutrophils were observed, i.e. to the same levels seen previously in stressed fish. 3. Functional analysis of peripheral blood leucocytes from cortisol-injected fish indicated that the remaining lymphocytes were no longer capable of responding to mitogenic stimuli. 4. This suppression of mitogenic stimuli was not seen when peripheral blood leucocytes were cultured in vitro with physiologic doses of cortisol. 5. This latter observation suggests that the cortisol alone was probably not directly responsible for the loss of responsiveness but possibly acted in vivo as an initiator of other events that eventually resulted in the observed immunosuppression.

Blood serum chemistry measurements of normal and acutely stressed channel catfish

1. An automated blood serum chemistry analytical system designed for human usage was employed to establish the levels of 26 different components present in sera obtained from various experimental groups of channel catfish. 2. Comparisons of samples from feral and commercial production pond fish during warm months indicated statistically significant differences in the serum levels of sodium, CO2, urea nitrogen, direct bilirubin, cholesterol, creatinine and protein. 3. Laboratory acclimated and production pond fish exhibited differences in serum electrolytes (sodium, potassium, chloride, phosphorus), serum metabolites (urea nitrogen, creatinine, triglycerides), serum enzymes [gamma-glutamyl transferase, glutamate-oxaloacetate transaminase (GOT), lactate dehydrogenase (LDH), alkaline phosphatase, and amylase], and serum iron. 4. Seasonal (temperature?) differences in production pond fish were noted for 12 serum components including potassium, magnesium, CO2, glucose, creatinine, albumin, iron, alkaline phosphatase, and glutamate-pyruvate transaminase (GPT). 5. Comparisons of samples obtained from laboratory-acclimated fish before and 18 hours after acute handling and transport stress revealed significant differences in only three serum parameters: glucose, LDH, and creatine phosphokinase (CPK). 6. These studies suggest that "normal" values established by any method of sera analysis may be different in the same species depending on the diet, season, and presence of environmental stressors.

Temperature-mediated processes in teleost immunity: the effects of temperature on membrane immunoglobulin capping on channel catfish B lymphocytes

1. In order to better understand ligand-induced redistribution of membrane receptors and lymphocyte activation in ectothermic vertebrates, flow cytometry was used to monitor the effects of both in vivo acclimation temperature and in vitro assay temperatures on the kinetics of monoclonal antibody-induced membrane immunoglobulin (mIg) capping on channel catfish lymphocytes. 2. It was observed that the kinetics of mIg capping were dependent on in vitro assay temperatures, in vivo acclimation temperatures, and the length of time of in vivo acclimation. In the latter situation in vivo acclimation of fish to 27, 22 and 17 degrees C was considered complete after 3 weeks, while acclimation to 12 degrees C required a minimum of 5 weeks. 3. The energies of activation required for mIg capping ranged from 33 to 24 kcal/mol; lower energies of activation were observed with lower temperature acclimation. 4. It was also noted that the lower energies of activation were associated with concomitant decreases in cellular phospholipid saturated/unsaturated fatty acid ratios. 5. It appears that channel catfish B cell mIg capping, presumably a requisite for immune function, can be significantly affected by environmental temperatures; most likely such effects are attributable to changes in plasma membrane viscosities.

Phylogeny of lymphocyte heterogeneity: the cellular requirements for the mixed leucocyte reaction with channel catfish

Vigorous mixed leucocyte reactions (MLR) were obtained using channel catfish peripheral blood leucocytes (PBL) when equal numbers of responder and stimulator cells (5 X 10(5) cells each) were cocultured. The use of 2000 rads of X-irradiation was sufficient to block subsequent proliferative responses of the stimulator cells. The cellular requirements for channel catfish MLR responses were assessed by using three functionally distinct leucocyte subpopulations isolated from the PBL. B cells (sIg+ lymphocytes) and T cells (sIg- lymphocytes) were isolated by an indirect panning procedure employing a monoclonal antibody specific for channel catfish Ig. A third population, monocytes, was isolated or depleted by adherence to baby hamster kidney cell microexudate-coated surfaces or adherence to Sephadex G-10, respectively. The results indicated that only the T cells were able to respond in the fish MLR, with monocytes being required as accessory cells. In contrast, all three cell types could function as stimulator cells. In addition, it was observed that low in vitro culture temperatures inhibited the generation of channel catfish MLRs, thereby supporting the contention that low temperature immunosuppression in fish results from a preferential inhibition of the generation of primary T-cell responses.

Temperature-mediated processes in teleost immunity: binding and mitogenic properties of concanavalin A with channel catfish lymphocytes

Low (non-permissive) temperatures inhibit the proliferation responses of channel catfish T cells to stimulation with Con A. The study reported here was undertaken to ascertain if failure to bind Con A at non-permissive temperatures could explain the observed suppression at such temperatures. The influence of temperature on the binding of fluorescein-labelled succinyl Con A to channel catfish T and B cells was studied by cytofluorography. The results indicated that Con A bound equally well at both mitogenically permissive (22 degrees, 27 degrees and 32 degrees) and non-permissive (12 degrees and 17 degrees) temperatures. Hence, temperature effects on mitogen-binding to cell surface receptors cannot readily explain the observed suppression of channel catfish T-cell proliferative responses at non-permissive temperatures.

The effects of in vivo acclimation temperature on the fatty acid composition of channel catfish (Ictalurus punctatus) peripheral blood cells

Channel catfish were acclimated in vivo to 12, 17, 22 or 27 degrees C and their peripheral blood erythrocytes, thrombocytes, T lymphocytes and B lymphocytes assayed for cellular fatty acid composition. Excepting cells from 12 degrees C acclimated fish, all cells responded to acclimation to lower temperatures by exhibiting increased levels of phospholipid unsaturated fatty acids. Although temperature independent differences were observed between erythrocytes, thrombocytes and lymphocytes, no differences between T lymphocytes and B lymphocytes were seen.

Phylogeny of lymphocyte heterogeneity: the cellular requirements for in vitro antibody responses of channel catfish leukocytes

Three functionally distinct leukocyte subpopulations were isolated from the peripheral blood of channel catfish. Surface immunoglobulin-positive (sIg+) and sIg- lymphocytes were isolated by an indirect "planning" procedure employing monoclonal antibodies specific for channel catfish Ig. A third population composed of macrophages was isolated by adherence to baby hamster kidney cell microexudate-coated surfaces. Functional features of these three cell types were established by assessing their role(s) in primary in vitro anti-hapten PFC responses to known murine thymus-dependent (TD) and thymus-independent (TI) antigens. The results indicated that anti-hapten PFC responses to a TI antigen required the presence of sIg+ lymphocytes and macrophages. In contrast, all three cell types were required for responses to TD antigens. Furthermore, the results of studies involving the depletion of antigen-reactive lymphocytes demonstrated that both hapten-specific sIg+ cells and carrier-specific sIg- cells were required for anti-hapten responses to TD antigens. These studies provide direct evidence that catfish have separable B cells (sIg+ lymphocytes), T helper cells (sIg- lymphocytes), and accessory cells (macrophages) quite similar to those seen in higher animals.

Phylogeny of lymphocyte heterogeneity: the cellular requirements for in vitro antibody responses of channel catfish leukocytes

Three functionally distinct leukocyte subpopulations were isolated from the peripheral blood of channel catfish. Surface immunoglobulin-positive (sIg+) and sIg- lymphocytes were isolated by an indirect "planning" procedure employing monoclonal antibodies specific for channel catfish Ig. A third population composed of macrophages was isolated by adherence to baby hamster kidney cell microexudate-coated surfaces. Functional features of these three cell types were established by assessing their role(s) in primary in vitro anti-hapten PFC responses to known murine thymus-dependent (TD) and thymus-independent (TI) antigens. The results indicated that anti-hapten PFC responses to a TI antigen required the presence of sIg+ lymphocytes and macrophages. In contrast, all three cell types were required for responses to TD antigens. Furthermore, the results of studies involving the depletion of antigen-reactive lymphocytes demonstrated that both hapten-specific sIg+ cells and carrier-specific sIg- cells were required for anti-hapten responses to TD antigens. These studies provide direct evidence that catfish have separable B cells (sIg+ lymphocytes), T helper cells (sIg- lymphocytes), and accessory cells (macrophages) quite similar to those seen in higher animals.

Phylogeny of lymphocyte heterogeneity: the cellular requirements for in vitro mitogenic responses of channel catfish leukocytes

Cell separation and enrichment techniques were employed to isolate three distinct leukocyte subpopulations present in channel catfish (Ictalurus punctatus) peripheral blood. Surface immunoglobulin-positive (sIg+) and sIg- lymphocytes were separated by an indirect "panning" technique employing monoclonal antibodies reactive with channel catfish Ig. A third cell population composed of macrophages was isolated by adherence to baby hamster kidney cell microexudate-coated surfaces. Functional features of these three subpopulations were assessed by in vitro mitogenic responses to lipopolysaccharide (LPS) and concanavalin A (Con A). The results that were obtained indicated that the sIg+ cells responded only to LPS stimulation regardless of the presence or absence of macrophages. The sIg- subpopulation, however, responded to neither LPS nor Con A unless macrophages were present, in which case responses were obtained to both mitogens. The accessory cell nature of the macrophages was shown by experiments utilizing fixed numbers of one cell type mixed with varying numbers of another cell type. Furthermore, the accessory cell function was abrogated by passage through Sephadex G-10 and preincubation with L-leucine methyl ester. These studies provide further evidence that teleosts not only contain B and T cells akin to those in mammalian systems, but contain accessory cells (macrophages) as well.

Phylogeny of lymphocyte heterogeneity: the cellular requirements for in vitro mitogenic responses of channel catfish leukocytes

Cell separation and enrichment techniques were employed to isolate three distinct leukocyte subpopulations present in channel catfish (Ictalurus punctatus) peripheral blood. Surface immunoglobulin-positive (sIg+) and sIg- lymphocytes were separated by an indirect "panning" technique employing monoclonal antibodies reactive with channel catfish Ig. A third cell population composed of macrophages was isolated by adherence to baby hamster kidney cell microexudate-coated surfaces. Functional features of these three subpopulations were assessed by in vitro mitogenic responses to lipopolysaccharide (LPS) and concanavalin A (Con A). The results that were obtained indicated that the sIg+ cells responded only to LPS stimulation regardless of the presence or absence of macrophages. The sIg- subpopulation, however, responded to neither LPS nor Con A unless macrophages were present, in which case responses were obtained to both mitogens. The accessory cell nature of the macrophages was shown by experiments utilizing fixed numbers of one cell type mixed with varying numbers of another cell type. Furthermore, the accessory cell function was abrogated by passage through Sephadex G-10 and preincubation with L-leucine methyl ester. These studies provide further evidence that teleosts not only contain B and T cells akin to those in mammalian systems, but contain accessory cells (macrophages) as well.

Temperature-mediated processes in teleost immunity: differential effects of temperature on catfish in vitro antibody responses to thymus-dependent and thymus-independent antigens

An in vitro culture system was employed to ascertain the effects of different temperatures on the anti-hapten antibody-secreting cell responses of channel catfish leucocytes to murine thymus-dependent (TD) and thymus-independent (TI) antigens. The magnitudes of primary responses to a TI antigen (TNP-LPS) and secondary responses to a TD antigen (DNP-KLH) were relatively independent of in vitro culture temperature. The kinetics of each of these responses as a function of temperature was characterized by a Q10 of 2. In contrast, the magnitudes of primary responses to TD antigens (DNP-KLH and DNP-HoSA) were suppressed at lower in vitro temperatures. Furthermore, it was observed that some of the low temperature suppression of primary responses to TD antigens could be abrogated by appropriate low temperature in vivo acclimation. These findings are interpreted as supporting the hypothesis that low environmental temperatures immunosuppress fish by virtue of differential inhibitory effects on the generation of carrier-specific helper cells.

Temperature-mediated processes in teleost immunity: differential effects of temperature on catfish in vitro antibody responses to thymus-dependent and thymus-independent antigens

An in vitro culture system was employed to ascertain the effects of different temperatures on the anti-hapten antibody-secreting cell responses of channel catfish leucocytes to murine thymus-dependent (TD) and thymus-independent (TI) antigens. The magnitudes of primary responses to a TI antigen (TNP-LPS) and secondary responses to a TD antigen (DNP-KLH) were relatively independent of in vitro culture temperature. The kinetics of each of these responses as a function of temperature was characterized by a Q10 of 2. In contrast, the magnitudes of primary responses to TD antigens (DNP-KLH and DNP-HoSA) were suppressed at lower in vitro temperatures. Furthermore, it was observed that some of the low temperature suppression of primary responses to TD antigens could be abrogated by appropriate low temperature in vivo acclimation. These findings are interpreted as supporting the hypothesis that low environmental temperatures immunosuppress fish by virtue of differential inhibitory effects on the generation of carrier-specific helper cells.

Microsystem for in vitro primary and secondary immunization of channel catfish (Ictalurus punctatus) leukocytes with hapten-carrier conjugates

Methods are described for the in vitro generation and detection of antibody-secreting cells (PFC) from channel catfish. Hapten-specific PFC can readily be enumerated by an indirect plaque assay employing rabbit antiserum to catfish Ig and guinea pig complement. A modified Mishell-Dutton-type culture system was developed for effectively generating significant in vitro anti-hapten PFC responses with catfish leukocytes at 27 degrees C. The classical hapten-carrier effect and primary responses to both TI and TD antigens were demonstrable with catfish cells. Variables found to be important with catfish cells included the serum supplement, cell densities and, to a lesser extent, antigen form. Optimistically these methods will prove useful in attempts to delineate the functional roles of different lymphocyte subpopulations in fish.