Relationships among differentiated T-cell subpopulations. I. Dissociated development of tuberculin type hypersensitivity, Jones-Mote type hypersensitivity and activation of helper function.

Relationships among tuberculin type hypersensitivity, Jones-Mote type hypersensitivity and activation of helper T cells were studied in AKR mice by means of footpad reaction, migration inhibition test and antibody production against the trinitrophenyl group. (1) Immunization with SRBC in saline, Freund's incomplete adjuvant (FIA) or complete adjuvant (FCA) and fixed-SRBC (FRBC) in FIA- or FCA-induced delayed hypersensitivity as demonstrated by footpad swelling. (2) Migration inhibition was positive in the groups immunized with SRBC or FRBC in FCA, but negative in those immunized with SRBC in saline or FIA or FRBC in FIA. This may suggest that the former has to be assigned to tuberculin type and the latter to Jones-Mote type. (3) Both pre-treatment with BCG and with cyclophosphamide (CY) augmented delayed footpad reaction in the mice immunized with SRBC in saline. However, migration inhibition was positive only in the group pre-treated with BCG. BCG may convert the reaction from Jones-Mote type to tuberculin type, while CY may augment the reaction of Jones-Mote type. (4) FRBC in saline scarcely induced delayed footpad reaction, whereas they activated helper function efficiently. Thus, three types of immunological phenomena attributable to the functions of T cells may depend upon distinct subpopulations of differentiated T cells which are raised by different methods of immunization.     

Induction of delayed hypersensitivity to protein antigens in mice without Freund adjuvants

Three ways for inducing tuberculin-type delayed hypersensitivity (DH) in mice to purified protein antigens without Freund adjuvant are described. Four strains of mice compared for susceptibility to sensitization with several antigens ranked SJL > CF-1 > CAF₁ = C57B1. Females were more easily sensitized than males. The first way of sensitizing without Freund adjuvant was simply to inject antigen intradermally in saline, but it could be used only with the potent antigen methylated human serum albumin (HSA). Six-mercaptopurine injections during the first 5 days of sensitization enhanced such sensitization in CF-1 but inhibited it in CAF₁ mice. The second way sensitized with a weaker antigen, chicken conalbumin (CA), and thus is more versatile. It consisted of injecting a saline solution of antigen into a 24-hr strong DH dermal reaction to an unrelated antigen (dextran). The third way was simplest and best: Freund adjuvant was replaced with aqueous Evans blue dye. Thus, distilled water solutions of antigen (CA or chicken ovalbumin) and dye injected subcutaneously induced DH indistinguishable from that induced with the same antigens in Freund adjuvant. Neither antigen in distilled water alone sensitized. The dye also intensified Arthus sensitization. This diazo dye therefore may be a practical, harmless water-soluble substitute for Freund adjuvant for inducing DH or cell-mediated immunity and for intensifying Arthus sensitization.     

Contact sensitivity to oxazolone in the chicken: evidence for Arthus type hypersensitivity of the cutaneous reaction.

Cutaneous hypersensitivity reaction can be induced in chickens by skin painting with oxazolone, 33 mg/Kg of body weight (KBW). The B cell contribution to the generation of the cutaneous reaction has been a matter of controversy. In an attempt to characterize this reaction we placed special interest on the possibility that the nature of this reaction could be Arthus type hypersensitivity. From the kinetics study on the cutaneous hypersensitivity after challenge with oxazolonated egg-albumin (EA-OX) it was excluded that the nature of this reaction could be delayed type hypersensitivity. Immune sera transfer experiments demonstrated that the cutaneous reaction was antibody dependent. Serum anti-oxazolone antibody titers in sensitized chickens were assayed by antiglobulin haemagglutination, using oxazolone coupled sheep erythrocytes (OX-SRBC). High titres of IgG were found in contact sensitized chickens. Furthermore this cutaneous reaction was characterized by neutrophils, inflammatory edema, rare thrombotic occlusion of small venules and on absence of monocytes. The utilization of complete Freunds' adjuvant (CFA) given at sensitization demonstrated that CFA enhanced oxazolone antibodies in the sera of immunized chickens without a correlated increase in the intensity of the cutaneous reaction to EA-OX. Animals sensitized to oxazolone (33 mg/KBW) without CFA and challenged intravenously seven days later with oxazolone coupled to autologous chicken red blood cells (OX-CRBC) died from anaphylactic shock; instead animals with the same treatment but with CFA given at sensitization did not die from anaphylactic shock. Taken collectively it was concluded that the cutaneous reaction to oxazolone in the chicken can be categorized as Arthus hypersensitivity. The relationship between cutaneous Arthus reaction and anaphylactic shock in chickens sensitized to oxazolone is discussed.     

Comparability of delayed hypersensitivity in various rodents. II. Jones-Mote type hypersensitivity in guinea-pigs immunized with sheep erythrocytes and its modification by cyclophosphamide or BCG pre-treatment.

Guinea-pigs were immunized via footpads with sheep red blood cells (SRBC) in saline. Histological examination of erythematous skin reaction was performed and effects of cyclophosphamide (CY) or BCG pre-treatment on the skin reaction were examined. Delayed-in-onset erythematous skin reaction accompanied by substantial basophil infiltration was elicited in guinea-pigs immunized with SRBC in saline. The erythema was augmented in size by CY which was injected 2 days before immunization. The reaction may be comparable to Jones-Mote type. In BCG pre-treated guinea-pigs, basophil infiltration at the skin reaction sites was reduced in number, but significant inhibition of macrophage migration was not detected in the presence of SRBC antigen. The reaction may be intermediate between Jones-Mote and the tuberculin type. Comparability of delayed skin reactions in guinea-pigs and delayed footpad reactions in mice or hamsters against SRBC is discussed.     

Enhancement of the Arthus reaction and suppression of delayed type hypersensitivity (DTH) by pluronic F-68, a detergent frequently used to prepare perfluorocarbon emulsions

The effect of a 20% w/v RM101 (perfluorobutyltetrahydrofuran) emulsion containing 5% w/v of the detergent Pluronic F-68 or 5% w/v Pluronic F-68 given alone on the Arthus reaction and on delayed type hypersensitivity (DTH) were evaluated in female A/J mice. The test substances were administered i.v. at 1% body weight at 0,4,7,14 and 28 days prior to the i.p. immunization with 10(7) sheep red blood cells (SRBC). The increase in footpad swelling at 4 h (Arthus reaction) and at 24 h (DTH) after elicitation with the s.c. administration of 10(8) SRBC into the left footpad was used to assess immune competence. Pluronic F-68 given alone enhanced the Arthus reaction only when administered on day 0 of immunization. Pluronic F-68 given alone, as well as the perfluorocarbon emulsion containing Pluronic F-68, suppressed the 24 h DTH for as long as 4 days prior to immunization. Nonemulsified perfluorocarbon, on the other hand, had no effect on either the Arthus reaction or on DTH. The immunostimulatory agent, levamisole, administered (10 mg/kg i.p.) 1.5-2 h prior to immunization with SRBC counteracted both the Arthus reaction and the DTH response produced by Pluronic F-68. The present data clearly demonstrate that the changes in Arthus reaction and the DTH response are due to the Pluronic F-68 used to emulsify the RM101 perfluorocarbon; the changes induced by the detergent in these two immune parameters probably involve separate mechanisms.     

Studies on delayed hypersensitivity to hepatitis b antigen in chimpanzees

Twenty-eight chimpanzees were divided into six groups according to their history of previous immunization or exposure to hepatitis B antigen (HBAg) and studied for delayed hypersensitivity (DH) to HBAg. Purified HBAg derived from a normal human carrier was used for in vivo skin testing and in vitro leucocyte migration inhibition tests. Of seventeen chimpanzees immunized with HBAg in Freund's complete adjuvant (FCA), nine exhibited positive DH reactions to HBAg with good correlation between the in vivo and in vitro responses. Of the seventeen chimpanzees, fourteen also exhibited positive DH reactions to purified protein derivative of tuberculin (PPD) with marked erythema and induration; the other three exhibited only erythema with no induration. None of the seventeen animals exhibited any immediate reactivity to either HBAg or PPD. Intradermal injection of HBAg-negative human serum failed to elicit DH reactions in four animals who showed positive skin test with purified HBAg; the DH response was thus probably HBAg-specific. Nineteen chimpanzees, including six unimmunized animals, three chronic carriers of HBAg and two which had been injected with HBAg without FCA, failed to show DH response to HBAg. Thus, DH to HBAg was observed only in animals hyperimmunized with HBAg in FCA.     

Relationships among differentiated T-cell subpopulations: II. Cytotoxicity and other functions of T cells specific for nucleated chicken erythrocytes

Relationships among T-cell mediated cytotoxicity, tuberculin type hypersensitivity, Jones-Mote type hypersensitivity and activation of helper T cells were studied in AKR mice by means of target cell destruction (⁵¹Cr-release), footpad reaction, migration inhibition test and antibody production against the trinitrophenyl group. (1) Immunization with chicken red blood cells (CRBC) in saline, Freund's incomplete (FIA) or complete adjuvant (FCA) and fixed-CRBC (FRBC) in FIA or FCA induced delayed hypersensitivity as demonstrated by footpad swelling. (2) Migration inhibition was positive in the group immunized with CRBC in saline or FCA, or FRBC in FCA, but negative in those immunized with CRBC or FRBC in FIA. This may suggest that the former has to be assigned to tuberculin type and the latter to Jones-Mote type. (3) T-cell mediated cytotoxicity by immune spleen cells was detected only in mice immunized with CRBC in saline. (4) Pre-treatment with cyclophosphamide augmented delayed footpad reaction in mice immunized with CRBC in saline, but suppressed cytotoxic activity. (5) FRBC in saline scarcely induced delayed footpad reaction and cytotoxic activity, whereas they activated helper function efficiently. Thus, four types of immunological phenomena, attributable to the functions of T cells, may depend upon distinct subpopulations of differentiated T cells which are raised by different methods of immunization.     

Contact Sensitivity to Oxazolone in the Chicken: Evidence for Arthus Type Hypersensitivity of the Cutaneous Reaction

Cutaneous hypersensitivity reaction can be induced in chickens by skin painting with oxazolone, 33 mg/Kg of body weight (KBW). The B cell contribution to the generation of the cutaneous reaction has been a matter of controversy. In an attempt to characterize this reaction we placed special interest on the possibility that the nature of this reaction could be Arthus type hypersensitivity. From the kinetics study on the cutaneous hypersensitivity after challenge with oxazolonated egg-albumin (EA-OX) it was excluded that the nature of this reaction could be delayed type hypersensitivity. Immune sera transfer experiments demonstrated that the cutaneous reaction was antibody dependent. Serum anti-oxazolone antibody titers in sensitized chickens were assayed by antiglobulin haemagglutination, using oxazolone coupled sheep erythrocytes (DX-SRBC). High titres of IgG were found in contact sensitized chickens. Furthermore this cutaneous reaction was characterized by neutrophils, inflammatory edema, rare thrombotic occlusion of small venules and on absence of monocytes. The utilization of complete Freunds' adjuvant (CFA) given at sensitization demonstrated that CFA enhanced oxazolone antibodies in the sera of immunized chickens without a correlated increase in the intensity of the cutaneous reaction to EA-OX. Animals sensitized to oxazolone (33 mg/KBW) without CFA and challenged intravenously seven days later with oxazolone coupled to autologous chicken red blood cells (OX-CRBC) died from anaphylactic shock; instead animals with the same treatment but with CFA given at sensitization did not die from anaphylactic shock. Taken collectively it was concluded that the cutaneous reaction to oxazolone in the chicken can be categorized as Arthus hypersensitivity. The relationship between cutaneous Arthus reaction and anaphylactic shock in chickens sensitized to oxazolone is discussed.     

Genetic determination of tuberculin hypersensitivity in chicken inbred lines

A dominant inheritance of the ability of CB line chickens to react to tuberculin over the inability of the WB line to develop this type of immune reaction was observed. The tuberculin reactivity in this line seems to be determined by one locus and is associated with the B locus. The involvement of the B locus in the regulation of tuberculin reactivity in other inbred lines of chickens is supported by the reactivity of the CA. IB (N6F2) birds in which the B allele of the IB line was introduced into the CA genotype. The CA. IB (N6F2) chickens manifest strong tuberculin sensitivity, corresponding to the type of reaction of the IB line, not to the weaker type of response of the CA line. The intensity of the tuberculin reaction of the CA and CC lines resembles that of the CB line, but the proportion of nonreactive birds is higher in these two lines than in CB chickens.     

Cellular and humoral immune responses in mice. II. Effect of intraperitoneal or subcutaneous injection of carrier of anti-hapten antibody and delayed hypersensitivity responses.

The subcutaneous (s.c.) injection of sheep red blood cells (SRBC) without adjuvant into mice preferentially induced delayed hypersensitivity (DH) reaction, as measured by footpad swelling, while intraperitoneal (i.p.) measured by the haemagglutinin test. Under these conditions, the properties of the helper activities of thymus-derived (T) cells for humoral responses were examined, in association with the features of the DH response, by measuring the anti-hapten and anticarrier antibody responses after a booster injection of trinitrophenylated (TNP) SRBC and by changing the combination of doses and injections routes of the carrier and the hapten-carrier conjugates. When mice were presensitized with i.p. injections of SRBC and boosted with i.p. injections of TNP-SRBC, the anti-TNP antibody production was maximally enhanced by presensitization with a low dose of SRBC, and gradually abolished with higher doses of SRBC for pre-sensitization. In the latter case, anti-SRBC antibody production was increases with increasing doses of SRBC..     

Immunological suppression of delayed hypersensitivity responses in mouse lungs as reflected by numbers of mononuclear cells, mast cells and mucus-producing cells

The suppression of delayed hypersensitivity (DH) in the lung as reflected by the appearance of mononuclear cells, mast cells and mucus-producing cells was studied in Balb/c mice. Immunosuppression was induced by intravenous and peroral administration of picrylsulfonic acid (PSA) in mice subsequently sensitized with picrylchloride (PiCl). The animals exhibited a decreased DH reactivity as assessed by ear thickness increase compared with mice sensitized but not exposed to PSA pretreatment. In mice exposed to PSA intravenously (suppressed) and sensitized with PiCl there was a decrease in the number of mononuclear cells in the lung after challenge, compared to mice sensitized and challenged only. Similarly, the mast cell and mucus-producing cell numbers were slightly lower in animals immunosuppressed intravenously with PSA compared with sensitized mice. Such a decrease in the numbers of mononuclear cells, mast cells and mucus-producing cells in the lung was not seen in animals treated with PSA perorally, although these animals exhibited suppressed DH reaction in the ears. The present results indicate that induction of mononuclear cells and to some extent mast cells and mucus-producing cells in the lung relates to the DH reaction and its regulation.     

Contact Sensitivity to Oxazolone in the Chicken: Evidence for Arthus Type Hypersensitivity of the Cutaneous Reaction

Abstract

Cutaneous hypersensitivity reaction can be induced in chickens by skin painting with oxazolone, 33 mg/Kg of body weight (KBW). The B cell contribution to the generation of the cutaneous reaction has been a matter of controversy. In an attempt to characterize this reaction we placed special interest on the possibility that the nature of this reaction could be Arthus type hypersensitivity. From the kinetics study on the cutaneous hypersensitivity after challenge with oxazolonated egg-albumin (EA-OX) it was excluded that the nature of this reaction could be delayed type hypersensitivity. Immune sera transfer experiments demonstrated that the cutaneous reaction was antibody dependent. Serum anti-oxazolone antibody titers in sensitized chickens were assayed by antiglobulin haemagglutination, using oxazolone coupled sheep erythrocytes (DX-SRBC). High titres of IgG were found in contact sensitized chickens. Furthermore this cutaneous reaction was characterized by neutrophils, inflammatory edema, rare thrombotic occlusion of small venules and on absence of monocytes. The utilization of complete Freunds' adjuvant (CFA) given at sensitization demonstrated that CFA enhanced oxazolone antibodies in the sera of immunized chickens without a correlated increase in the intensity of the cutaneous reaction to EA-OX. Animals sensitized to oxazolone (33 mg/KBW) without CFA and challenged intravenously seven days later with oxazolone coupled to autologous chicken red blood cells (OX-CRBC) died from anaphylactic shock; instead animals with the same treatment but with CFA given at sensitization did not die from anaphylactic shock. Taken collectively it was concluded that the cutaneous reaction to oxazolone in the chicken can be categorized as Arthus hypersensitivity. The relationship between cutaneous Arthus reaction and anaphylactic shock in chickens sensitized to oxazolone is discussed.     

Effect of hydrocortisone, cyclophosphamide, azathioprine and methotrexate on cutaneous delayed and arthus hypersensitivity in the rat.

The effect of 4 immunosuppressive agents--hydrocortisone (HC), cyclophosphamide (CY), azathioprine (AZ) and methotrexate (MTX)--, on cutaneous delayed-type hypersensitivity (DTH) and Arthus reactions to the intradermal injection of ovalbumin (OA) in rats sensitized to OA in Freund's complete adjuvant (FCA) was studied. Multiple doses (daily for 4 days) were given either early, beginning on the day of sensitization, or late, beginning 9 days after sensitization. Single doses were given on the day of challenge with OA. All late multiple doses of drugs except HC depressed the DTH at 24 h in the following order of decreasing magnitude: MTX, CY, AZ. The DTH at 24 h was depressed by early multiple doses of MTX at all doses, by CY at all but the lowest dose, and by AZ at the intermediate dose; HC had no effect. When the drugs were given as single late doses, only CY at the lowest dose and MTX at the higher doses effectively depressed the DTH at 24 h. Increased Arthus reactions occurred after early and late multiple doses of HC and after a late single dose of CY at the highest dose. After late multiple doses the Arthus reaction was unaffected by either CY or MTX but was depressed by all doses of AZ. HC administered as 3 injections around the time of challenge markedly depressed the delayed and Arthus reactions. These results show that each of the 4 immunosuppressive drugs could depress DTH and Arthus reaction to OA, but the degree of depression varied with the time of drug administration relative to sensitization and challenge, and the dose of drug used. Histologic examination of skin test sites showed that an apparently negative reaction did not necessarily imply total absence of a cellular inflammatory response.     

Delayed (footpad) hypersensitivity and Arthus reactivity using protein-rich antigens and LPS in mice immunized with live attenuated aroA salmonella vaccines

Footpad reactions to protein-rich salmonella extracts and lipopolysaccharide (LPS) were studied in BALB/c mice 2 and 8 months after immunization with the Salmonella typhimurium SL3261 aroA live vaccine. T-cell depletion in vivo and adoptive serum transfer showed that protein-rich antigens induced T-cell dependent delayed hypersensitivity reactions, whereas LPS only elicited Arthus reactions. The footpad reactions to crude protein extracts were not always T-cell mediated, but depended on the nature and the dose of the antigen. Selective depletion of CD4⁺ T cells alone had a greater effect than depletion of CDa⁺ T cells alone, but neither was as marked as simultaneous depletion of both CD4⁺ and CD8⁺ T cells, which abolished the delayed type hypersensitivity (DTH) response.Crude protein-rich extracts subjected to alkaline hydrolysis (which removes some ester-linked fatty acids and causes disaggregation of LPS resulting in decreased toxicity while conserving O-specificity) still gave positive T-cell dependent reactions, but with reduced T cell independent reactivity.Purified phenol-water LPS (2.5 μg) produced Arthus reactivity which could be confused with DTH. LPS induced positive reactions which still occurred in T-cell depleted mice and were transferable by immune serum. Arthus reactions did not occur when using alkali-treated LPS, which showed reduced complement fixation in vitro when using serum from immunized mice.The results indicate that footpad testing using salmonella antigens containing LPS elicit DTH but can also produce toxic reactions, some of which are T-cell independent and not necessarily a true measure of DTH. Arthus reactivity to LPS can be confused with DTH. Alkaline hydrolysis of the antigens can eliminate non-specific reactogenicity while retaining the ability of the (protein-rich) antigen to elicit a true T-cell dependent footpad response, which requires the participation of both CD4⁺ and CD8⁺ T cells.     

Soluble factors in immune sera of mice. I. Specific and non-specific suppressive activity.

Serum collected from mice 7 days following immunization with heterologous erythrocytes (SRBC, HoRBC) contained potent and specific immunosuppressive activity. When the serum was filtered through a Diaflo UM-10 membrane the activity was recovered in the filtrate, indicating that a factor less than 10,000 Daltons is responsible for it. Filtrates obtained from animals immunized with soluble antigens (BSA, POL) in FCA suppressed the 7S response to SRBC but had no effect on the 19S response. This non-specific suppressive effect on the7S response was also shown by filtrates obtained from sera of animals injected with FCA or other adjuvants (LPS, poly A:U). The 19S response to SRBC was either not affectd (LPS, poly A:U) or actually enhanced. (FCA). The SRBC-induced filtrates markedly suppressed the espression of DH to SRBC.     

The structural basis of cell-mediated immunological reactions of collagen: Characteristics of cutaneous delayed hypersensitivity reactions in specifically sensitized guinea-pigs

Cell-mediated immunological properties of collagen were studied in guinea-pigs employing cutaneous delayed hypersensitivity reactions. The animals were sensitized by a single injection of highly purified native collagen in Freund's complete adjuvant (FCA). Reactivity could be induced with 150 μg of calf collagen. Maximal reactivity was obtained 20 days after sensitization and persisted for more than 3 months. Histologically, the reactions displayed the typical features of delayed reactions with infiltration of predominantly mononuclear cells. No reactivity was induced in animals injected with FCA alone, with collagen in Freund's incomplete adjuvant (FIA), or with guinea-pig collagen in Freund's complete adjuvant. Reactivity was impaired when carrageenan was injected intraperitoneally at the time of challenge. Cyanogen bromide digested collagen was still reactive in sensitization as well as in elicitation. The reaction was found to be species specific in the sense that maximal reactions were obtained when the challenging collagen was from the same species as the sensitizing preparation. In vitro, denatured rat collagen was found to inhibit the migration of macrophages from specifically sensitized animals. By alterations of the immunization schedule antibodies, reactive with collagen in a haemagglutination system, could be induced.

The system lends itself to a comparative investigation of the structural requirements on a natural protein for the induction of the cell-mediated and the humoral immune response.

     

Dimethyl diotadecyl ammonium bromide as adjuvant for delayed hypersensitivity in mice.

Immunization of mice with antigen mixed with cationic surface active lipid dimethyl dioctadecyl ammonium bromide (DDA) produced delayed type hypersensitivity (DH), measured as a footpad swelling. The DH to sheep red blood cells or dinitrophenyl conjugated with bovine serum albumin (DNP28-BSA) in DDA exceeded the response of the same antigens in Freund's Complete Adjuvant (FCA) significantly. Treatment of mice with CY 8 hr prior to the injection of antigen in FCA or DDA resulted in delay of the onset of footpad swelling past day 5 and in elimination of the differences in the response due to the adjuvants. Immunization with carrier or hapten-carrier complexes with different epitope density in DDA and elicitation with the homologous and heterologous antigens revealed that the DH was DNP-specific. In vivo priming with DNP28-BSA in DDA and in vitro stimulation with the same antigen resulted in peak responses which were twice as high and were reached almost twice as fast as the earlier found response following immunization in FCA. The advantages of DDA as adjuvant over covalently linked fatty acid chains and over FCA are discussed.     

Regulation of the delayed hypersensitivity reaction in the lung reflected as mononuclear, mast cell and mucus cell appearance after T helper cell depletion and adoptive transfer

Epicutaneous sensitization with picrylchloride (PiCl) induced a strongly delayed hypersensitivity (DH) reaction in mice. Local challenge in the airways of these mice resulted in increased numbers of mononuclear cells, mast cells and mucus cells. Depletion of T helper cells in vivo by treatment with monoclonal antibody (GK 1.5) inhibited the DH reaction. This treatment also resulted in a decrease in the number of mononuclear and mucus cells in the lung after intranasal challenge. The DH reaction was transferred to recipients with immune lymph node cells and spleen cells from mice sensitized epicutaneously with PiCl. The recipient mice also showed a slight increase in the number of mononuclear cells in the lung after intranasal challenge. These results indicate that T cells are not only involved in the DH reaction but also in the accompanying lung reaction.     

Cellular immune response to sheep erythrocytes: interrelationship between proliferation of popliteal lymph node cells and footpad swelling

Mice were sensitized with graded doses of sheep erythrocytes by the intravenous or subcutaneous route and challenged for delayed-type hypersensitivity (DTH) at different times thereafter. The DTH response as assessed by footpad swelling (FPS) was compared to the spontaneous proliferative response of the popliteal lymph node cells (PLNC). Proliferation of PLNC was optimal after sensitization regimens resulting in optimal FPS. The same was true for mice sensitized under cyclophosphamide modulation. Proliferation of PLNC induced by SRBC was antigen-specific, although some crossreactivity with horse red blood cells was observed. Proliferation of PLNC could be abrogated by treatment with anti-Thy-1.2 antiserum plus complement demonstrating the T cell nature of proliferating cells. In accordance with published data, FPS of mice presensitized with a high dose of SRBC as well as FPS of recipients of spleen cells from high-dose-sensitized donors was suppressed. In marked contrast, PLNC proliferation was not diminished in these mice. Although proliferation of PLNC did not parallel FPS under all circumstances, it seems to be a correlate of the cellular immune response to SRBC.     

The Loss of Macrophages from Peritoneal Exudates following the Injection of Antigens into Guinea-Pigs with Delayed-Type Hypersensitivity

Exudates were induced in the peritoneal cavities of guinea-pigs by the injection of glycogen. The cell content of these exudates was examined after 4 days in normal and hypersensitive animals. In animals uninjected with antigens, the exudates contained a high proportion of macrophages, together with lymphocytes and polymorphs. In BCG-vaccinated animals, with delayed-type hypersensitivity to tuberculin, subcutaneous, intravenous or intraperitoneal injection of tuberculin resulted in a profound fall in the macrophage content of the exudates. This effect was apparent within an hour of intraperitoneal injection and occurred with very small doses of tuberculin. No such effect occurred after the intraperitoneal injection of tuberculin into guinea-pigs with Arthus hypersensitivity to tuberculin. Ovalbumin injected intraperitoneally into guinea-pigs with mixed delayed-type and Arthus hypersensitivity to ovalbumin also resulted in a marked fall in the macrophage content of peritoneal exudates, but had no effect on the peritoneal macrophages of animals with pure Arthus hypersensitivity. Bacterial endotoxin injected intraperitoneally caused a similar fall in the macrophage content of exudates of both normal and BCG-vaccinated animals. It is concluded that this loss of macrophages from peritoneal exudates after the injection of antigen is the consequence of an immunological reaction which is a manifestation of a state of delayed-type hypersensitivity.