Requirement for lymphocytes and resident macrophages ... - CiteSeerX

12 downloads 0 Views 1MB Size Report
Pleurisy was induced in ether-anesthetized animals by the intrathoracic. (it.) injection of LPS. (250 ng/cavity) in a final volume of 100 il. Experiments included.
Requirement

for lymphocytes

LPS-induced

pleural

and

eosinophil

resident

macrophages

accumulation

Patricia T. Bozza, Hugo C. Castro-Faria-Neto, Carmen Penido, Maria das Gra#{231}as,M.O. Henriques, Patricia M.R. Silva, Marco Ricardo Ribeiro dos Santos and Renato S.B. Cordeiro Departamento

de Fisiologia

Cruz/FIOCRUZ,

Rio

e Farmacodindmica

de Janeiro,

and

*Departamento

. eosinophils

. icrophages

of

e Biologia

have demonstrated neutrophils and

lasting

significantly inhibited the eosinophilia triggered by LPS. The i.t. injection of liposomes containing dichboromethylene diphosphonate significantly reduced (65%) the number of resident macrophages after 5 days. Under this condition, the eosinophil infiltration induced by LPS was completely inhibited. Accordingly, the i.t. injection of supernatant from macrophage monolayers, obtained from the pleural cavities of LPS-injected rats, into naive recipient animals led to a twofold increase in the number of pleural eosinophils. In conclusion, our data suggest an important role for resident macrophages and T bymphocytes in the eosinophil accumulation induced by LPS. J. Lcukoc. Biol. 56: 151-158; 1994. (LPS)

de Bioquimica

We tion

trathoracic (i.t.) injection of LPS (250 ng/cavity) into rats induced a significant eosinophil accumulation that developed within 24 h, was maximal at 48 h, and returned to control values within 120 h. This eosinophil influx was preceded by a huge neutrophil influx within 4 h and accompanied by a mononuclear cell accumulation between 24 and 48 h. Pretreatment with an antineutrophil monocbonal antibody (RP-3, 2 ml per animal) selectively reduced the number of circulating neutrophils within 8 h but failed to alter the LPS-induced eosinophilia. Similarly, platelet depletion with an anti-rat platelet antiserum did not alter the LPS-induced eosinophil accumulation. Cycbosporine (.50 mg/kg, 12 and 2 h before) partially inhibited (51%) the LPS-induced pleural eosinophilia, whereas the eosinophilia was not changed by prior degranulation of pleural mast cells with polymyxin B (10 tg/cavity, 24 h before). Moreover, selective depletion ofT lymphocytes using an anti-Thy 1.0 monocbonal antibody

endotoxin

Andrea P. Larangeira, A. Martins, Molecular,

. T

rat

and

dose-dependent

pleural

in

cavity.

vitro,

that LPS, mononuclear

indicating

INTRODUCTION

LPS

that

the

characterized [ 2-4], later

by

an

infiltration

induced

by

within

acute

neutrophil

influx

followed by mononuclear phase of the reaction

cell

accumulation

[5].

LPS

during

is

2-3

h the

to the migrainduces a long’ in

to attract

the

eosinophils

observed

in

generated endogenously accumulation was

vivo

is

[6]. Inprevented

by glucocorticosteroids and a protein synthesis inhibitor but not by platelet-activating factor (PAF) antagonists or inhibi’ tors of arachidonic acid metabolites [7]. Moreover, it was demonstrated that the cell-free pleural washings from LPSinjected rats contained a heat-stable protein that induces selective eosinophil accumulation in naive recipient animals [7]. The aim of this study was to investigate the cell source of LPS-induced eosinophil chemotactic factor. By means of selective cellular depletion, we provide evidence for the involvement

of

sinophil

T

lymphocytes

accumulation

MATERIALS

and

induced

macrophages

by

in

the

eo-

LPS.

AND METHODS

Animals Male ing

Wistar 18-25

rats

weighing

150-180

Cruz

Foundation

g (Oswaldo

g and

Swiss

breeding

mice unit)

weigh-

were

used.

Pleurisy Pleurisy was induced in ether-anesthetized intrathoracic (it.) injection of LPS (250 volume of 100 il. Experiments included of control line. The

animals animals

animals ng/cavity) equivalent

receiving the same were killed with an

volume overdose

by the in a final numbers

of sterile of ether

saat

different times (1-24 h) after the it. injection of LPS or saline, and the thoracic cavity was washed with 3 ml of heparinized saline (10 Ui/mb) and the fluid volume evaluated with a graduated syringe. Total leukocyte counts were per-

on

cytocentrifuged

Gr#{252}nwald-Giemsa

Leukocyte

Oswaldo

accumulation

failed

eosinophilia

accounted for by a factor(s) deed, LPS-induced eosinophil

performed

Lipopolysaccharides (LPS) of the cell wall of gram-negative bacteria elicit a wide range of effects on biological systems and mimic several of the pathophysiobogical events observed during infections with these organisms (for a review see ref. 1). One of the hallmarks of the inflammatory response induced by LPS is its attraction of leukocytes to the focus of

in addition cells,

eosinophil

However,

formed in a Coulter counter after ing with isotonic liquid. Differential

inflammation.

Instituto

Brazil

Abstract: In this study we investigated the involvement of inflammatory cells in the pleural accumulation of eosinophils induced by lipopolysaccharide (LPS). In-

Key Words: lymphocytes

in

Abbreviations: lene

APAS,

PAF, blood

red

Reprint

anti-rat

mAb, TNF-a,

requests:

tumor

PT

Fundac#{227}o Oswaldo

Bozza,

Cruz,

Cl2MD1

antibody;

necrosis

NRS,

factor

dichloromethyLPS,

normal

rabbit saline;

Journal

December

of Leukocyte

2,

1993;

Biology

accepted

seRBC,

a.

de Fisiologia e Farmacodin#{226}mica, Rio de Janeiro, Rj 21045 900,

Brazil.

Received

May-

performed

interleukin’8;

phosphate-buffered

Departamento Av. Brasil 4365,

washwas

the

were

IL-8,

PBS,

by

counts

antiserum;

interferon’y; factor;

pleural analysis

stained

cell

platelet

monoclonal

platelet-activating cell;

Mast

IFN-’y,

lipopolysaccharide; rum;

smears

method.

diphosphonate;

diluting the leukocyte

March

Volume

21,

56,

1994.

August

1994

in a Neubauer

chamber

ing

fluid

the

Allergic

pleural

under

light

in toluidine

blue

microscopy

after

Pleural

dilut-

dye.

The animals were sensitized subcutaneously with a mixture ovalbumin (50 tg) and aluminum hydroxide (5 mg) in a final volume of 200 gil. Fourteen days later ovalbumin (12 pg/cavity) was administered it. and after 24 h the were killed Nonsensitized it. were used

Blood

cell counts

and

pleurisy animals as negative

transfer

was evaluated as in which ovabbumin controls.

.

.

.

.

Six hours after the i.t. injection of LPS line into donor rats, the pleural cavity jl of sterile saline, and the pleural (400g) for 10 mm at 4#{176}C.The pleural

pleurisy

animals above. jected

washing

.

15

>-

described was in-

(250 ng/cavity) or sawas washed with 500 fluid was centrifuged wash free of cells was

I-. *

C.)

12

A

*

‘0 9.

Blood samples were obtained from the tail vein 3 or 8 h after administration of antiplatelet antiserum or antineutrophil monocbonal antibody (mAb), respectively. The samples were diluted in Turk fluid (2% acetic acid) for total leukocyte counts or in buffered EDTA-formalin solution for platelet and red blood cell (RBC) counts. Buffered ELffA-formalin solution was prepared by adding 3 ml of 0.077 M EDTA, ml of 10 x concentrated phosphate-buffered saline (PBS), 150 l of 40% formalin, and distilled water to a final volume of 20 ml. The counts were performed in Neubauer chambers under light microscopy. Differential analysis was performed in blood smears stained by the May-Gr#{252}nwald-Giemsa method.

Co

< Ui 1

0 2

z 0 z

.

0

0’

20

*

>-

I-

Treatments Specific neutrophil depletion was achieved 8 h after the intraperitoneal injection of anti-rat neutrophil mAb (RP-3, 2 ml per animal) [8]. The ascites of a nonhybridized parent cell line, P3-X63.Ag8.653, was used as a control. Platelets

C.)

15

B

#{149}0

*

were depleted by an intravenous (iv.) injection of a rabbit anti-rat platelet antiserum (APAS) 3 h before the LPS injection. Control animals received an i.v. injection of a normal rabbit serum (NRS). T lymphocyte depletion was achieved

*

by the treatment ofmice with a rat anti-murine Thy 1.0 mAb (G7, American Type Culture Collection, Rockvible, MD). The supernatant of the G7 hybridoma was semipurified and 20 x concentrated by ultrafiltration (Amicon, Beverly, MA) with a 100-kDa cutoff membrane. The retentate, after being further washed with five volumes of PBS to help deplete substances smaller than 100 kDa, was injected intraperitoneally (100 l) daily during 6 days. The mice were used 24 h after the last injection ofthe antibody. The success ofT cell depletion was ascertained by immunoperoxidase staining of spleen cells, and the depletion was greater than 90% after the end of the treatment. Polymyxin B (10 tg/cavity) was used as a mast cell degranulating agent [9], and was injected intrathoracically 24 h before LPS. Cycbosporine (25-50 mg/kg) injection.

was given orally Cycbosporine

12 and 2 h before the LPS or antigen was solubilized with corn oil, and the

vehicle was administered biposomes were prepared 75 mg of phosphatidylcholine dissolved in chloroform.

to control groups. Encapsulated as described earlier [10]. In brief, and 11 mg of cholesterol were The thin film that formed after ro-

4

3

2

tary evaporation was dispersed by 10 ml of PBS. For dichboromethylene diphosphonate (C12MDP)-containing liposomes, 1.9 g of CI2MDP was dissolved in the 10 ml of PBS in which the lipid film had been dispersed. After being washed, the liposomes were resuspended in 4 ml of PBS, and 0.1 ml (containing about 1 mg of liposome-entrapped C12MDP) was injected i.t. in the rat. Macrophage ebimination in situ was obtained 5 days after an it. injection of C12MDP-containing liposomes. Control animals received PBS-containing liposomes.

152

Journal

of Leukocyte

Biology

Volume

56,

August

1994

0 0

24

12

48

72

TIME Fig. 1. Time (C) accumulation

( 250 for

course in

at

least

eight by

the

(#{149}) or

ng/cavity)

indicated

ofmononuclear

an

animals. asterisk.

cell

pleural saline

cavity (0).

Statistically

Results

(A),

96

(H)

neutrophil

induced are significant

120

by

(B), the

it.

expressed differences

and

eosinophil

injection as

of

(P

LPS

± SEM

means
.

>

diphosphonate (Germany).

C) ‘0 SC

Statistical

analysis

Data are statistically bowed by significance

C,)

reported as means by means of analysis the Newman-Keuls-Student set at P < .05.

± SEM and were analyzed of variance (ANOVA) foltest with the level of

RESULTS

x 0. 0

z (I,

0 Lii

stimulus

SAt.

LPS

LPS

LPS

SAL

LPS

triatmmtl

-

-

XP3

RP-3

-

-

Fig.

2. Effect

eosinophil

Time course The

it.

neutrophil numbers mononuclear

of cell accumulation

injection

of LPS

accumulation of neutrophils cell

(Fig.

(250

induced

ng/cavity)

induced

within declined

4 h (Fig. 1B). and significant

1A)

eosinophib

and

The

by LPS

(Fig.

At

24

increases 1C)

antineutrophil

(XP3)

a marked h,

the in

counts

of the

from

mAb

the

traperitoneally platelet

(P




by

mast cell or enhance

degranulation the eosinophil

with polymyxin accumulation

B in-

LPS.

+

3

0

Effect of cyclosporine treatment and lymphocyte depletion on the LPS-induced eosinophil accumulation

“5.

0 >



I>

ofcyclosporine

± SEM

(P

(B), br




Cells

+ Cells



-

Fig.

it.

and

[10]. resident

through

accumulation

demonstrated LPS-injected

mice

treatment without

liposomes. the

sinophil

in

this

monocytes of pleural

cells

indicate the LPSway to iden-

in

work is under for this effect. intravenous injection induced pronounced

that

eosinophil

LPS-induced

results

role

macrophages,

of circulating the involvement

depletion

our

important

depletion

to point

against

number verified

depleted in vivo of 1’ lymphocytes by means of an anti-Thy 1.0 mAb. Eosinophil accumulation induced by LPS in mice shows the same pattern of response as that observed in rats and also seems to depend on a newly generated heat-stable protein [11]. In agreement with the data obtained with cycbosporine in rats, T lymphocyte depletion with anti-Thy 1.0 mAb in mice was very potent in inhibiting eosinophil migra-

=

an

macrophage

C12MDP-containing

< 0

as a whole,

play

is interesting

only

least

differences

liposome-treated

by

lymphocytes

long-basting

given

liposomes

SEM

groups.

and

those

significant

saline-challenged

(250 fluid

respectively. for

C12MDP

tsseans

statistically

LPS pleural

T

induced eosinophilia, and further tify the T cell subset responsible It has been reported that C12MDP-containing liposomes

eosinophilia

the

h

eosinophilia expressed

plus

C12M an

24 columns

(striped

Results

the before

LPS-challenged fluid

liposomes

column).

solid

and

pleural

on

5 days

it.

performed

and

saline-

PBS-containing

eight

given

were open

rats,

( crosshatched

CI2MDP

were

The

LPS-challenged

control

containing

Liposomes

ng/cavity)

For

induced

that

induced

(P

iCY’

x

SAL-m#{216}

of

with

asterisk,

LPS-challcngecl

l)leral

wash

fluids.

Biology

Volume

56,

August

several

main

liposonse-treated

stimulation

1994

target

other cell

[1, 30,

reports for

31].

showing cytokine

that production

macrophages following

are

the LPS

Both

lymphocyte

and

macrophage

depletion

IL-5 accounts for the mouse triggered by antigen but not

completely

abolished the LPS-induced eosinophil migration, suggesting that cooperation between these cells might take a place in this reaction. Indeed, T cell bymphokines can regulate macrophage activation and lead to the production and secretion of cytokines. For example, a T cell supernatant and IL-2 are

12.

able to necrosis

13.

induce factor

macrophage (TNF)

production of [32-34]. Moreover,

IL-i

or IL-2

tumor and

interferon-y (IFN-’y) enhance the production of TNF-a, TNF-f3, IL-i, and IFN-’y by monocytes and macrophages in the presence of LPS or cytokines [35-37]. Nevertheless, the precise mechanisms of cooperation between lymphocytes and macrophages for the production of LPS-induced eosinophibotactic factor are still not clear and studies are under way to further clarify this point. In conclusion, our results indicate that cumulation induced by LPS is independent neutrophils, and platelets. Furthermore, resident macrophages seem to contribute of the eosinophil chemoattractant protein

eosinophil acof mast cells, lymphocytes and to the production induced by LPS.

D.S., Dessein, Characterization

Silberstein,

JR.

(1987)

that

enhances

mansoni El-Cheikh,

A.J.,

toxicity

J.

Immunol.

MC.,

of

Dutra,

Elsas,

M.,

Saliou,

Elsas,

B.,

15.

16. Strieter,

P.,

T.J.,

disparate

Joseph,

D.,

MM., inflammation

Issekutz,

AC., induced

Movat, by E.

HZ. in

co/i

(1980) rabbits.

19.

Am.

21.

J.

Pathot. 98, 485-498. 3. Colditz, 1G., Movat, HZ. (1984) Kinetics of neutrophil accumulation in acute inflammatory lesions induced by chemotaxins and chemotaxinigens.j Immunol. 133, 2169-2173. 4. Cybulsky, MI., Chan, M.K., Movat, HZ. (1988) Acute inflammation and microthrombosis induced by endotoxin, interleukin-1, and tumor necrosis factor and their implication in gram-negative infection. Lab. Invest. 58, 365-378. 5. Issekutz, TB., Issekutz, AC., Movat, HZ. (1981) The in vivo quantitation and kinetics of monocyte migration into acute inflammatory tissue. Am. j Pathol. 103, 47-55. 6. Bozza, PT., Castro-Faria-Neto, H.C., Pires, ALA., Silva, P.M.R., Martins, MA., Cordeiro, R.S.B. (1991) Endotoxin induces eosinophil accumulation in the rat pleural cavity. Braz. j Med. Biol. Res. 24, 957-960. 7. Bozza, PT., Castro-Faria-Neto, H.C., Martins, MA., Larangeira, A.P., Perales, J.E., Silva, P.M.R., Cordeiro, R.S.B. (1993) Pharmacological modulation of lipopolysaccharide-induced pleural eosinophilia in the rat; a role for a newly generated protein. Eur. j Pharmacot. 248, 41-47. 8. Sekiya, S., Gotoh, S., Yamashita, T., Watanabe, T, Saitoh, S., Sendo, F. (1989) Selective depletion of rat neutrophils by in vivo administration of a monoclonal antibody. J. Leukoc. Biot. 46, 96-102. 9. Cabado, AG., Vieytes, MR., Botana, L.M. (1993) Rat pleural and peritoneal mast cells stimulated at different cellular levels: difference in and influence of purification media. mt. Arch. Atlergy Immunol. 100, 234-239. 10. Van Rooijen, N., Van Nieuwmegen, R. (1984) Elimination of phagocytic cells in the spleen after intravenous injection of liposome-encapsulated dichloromethylene diphosphonate. Ce/I Tissue 11.

Res.

Bozza, PT, A.P., Silva,

238,

22.

Kasahara, Kunkel,

K., S.L.

chemotactic

of

H.C., MA.,

Penido, Cordeiro,

C.,

Larangeira, R.S.B. (1994)

(1991)

Eosinophil

in schistosomal Lab. Invest. 64, N.,

23. 24.

Bachelet,

Induction

Allen,

(1990)

factor

guinea

ca-oxidation

pig

CM.,

of

R.,

eosinophil

products

Showell,

Human

gene

Bozza,

PT,

of

on

J.

Borel,

in vivo B4 and

5-11. Watson, ML., Moqaccumulation induced in vivo. Immunology

Silva,

MA., pleu

and

leukotriene

30,

H.C.,

Martins,

Biophys.

AR.,

Cordeiro,

ral

Larangeira,

R.S.B.

neutrophil

(1994)

accumulation

marrow

neutrophils and platelet-activating factor. 270, 143-149. Y.A., Doorschner, Al., Mallet, E. (1992) Cytokine released by thrombin-stimulated platelets is a potent for human eosinophils. j Exp. Med. 176, 587. D.C., Raziuddin, S. (1982) Lipopolysaccharides and In Immunopharmacology (P. Sirois and M. Rolaeds), (Elsevier Biomedical, Amsterdam, 169-199.

Pharmacot.

Kameyoshi, RANTES attractant Morrison, endotoxin. Pleszczynski, Spry,

In vitro

towards

Prostagtandins

P.M.R.,

Stanexhibit

Biochem.

R. (1985)

Castro-Faria-Neto,

Silva,

H.J.,

neutrophils

expression.

leukocytes

products.

C.J.F.

(1988)

to the Scien4/lc UK. J.F.

Eosinophils:

and Medical

(1989)

Pharmacology properties

Padova,

FED.

(1989)

A Comprehensive

Literature.

IV. Pharmacological mune).

in

Pharmacot.

Rev.

and

University,

ofcyclosporine vivo. Pharmacot. of

effects 41,

Review,

Oxford

Pharmacology

V. Pharmacological

studies.

Guide

Oxford,

(Sandimmune). Rev. 41, 259-351.

cyclosporine

ofimmune

(Sandim-

function:

in vitro

373-405.

25.

Iwamoto, I., Tomoe, S., Tomioka, H., Takatsu, K., Yoshida, S. (1992) Role of CD4 T lymphocytes and interleukin-5 in antigen-induced eosinophil recruitment into the site of cutaneous late-phase reaction in mice. j Leukoc. Biot. 52, 572-578.

26.

Kaneko,

M.,

Hitoshi,

Y.,

Matsumoto,

S.

(1991)

Role

of

interleukin-5

27.

28.

in local accumulation of eosinophils in mouse allergic peritonitis. Int. Arch. Allergy AppI. Immunol. 96, 41-45. Nakagima, H., Iwamoto, I., Tomoe, S., Matsumura, R., Tomioka, H., Takatsu, K., Yoshida, S. (1992) CD4 T-lymphocytes and interleukin-5 mediate antigen-induced eosinophil infiltration into the mouse trachea. Am. Rev. Respir. Dis. 146, 374-377. Amon,

EU.

(1992)

from human Agents Actions 29.

Huitiga,

Cyclosporin

A

peripheral basophils Special conference

I., Van

Rooijen,

N.,

inhibits

and Issue,

Groot,

histamine

human skin C250-C252.

C.J.A.,

release

mast

Uitdehaag,

cells. B.M.J.,

Dijkstra, CD. (1990) Suppression of experimental allergic encephalomyelitis in Lewis rats after elimination of macrophages. j Exp. Med. 172, 1025-1033. 30. Mathison, J.C., Virca, GD., Wolfson, N., Tobias, P.S., Glaser, K., Ulevitch, R.J. (1990) Adaptation to bacterial lipopolysaccharide

(LPS)

production 31.

355-358.

Castro-Faria-Neto, P.M.R., Martins,

Schistosoma

marrow cultures by heat-stable macrophages. Allergy 47, 142.

Res. Commun. 173, 725. Czarnetzki, B.M., Mertensmeier,

A.P.,

Sci. Am. Kinetics

Havet,

(1992)

18. Collins, PD., Weg, V.B., Faccioli, L.H., bel, R., Williams, T.J. (1993) Eosinophil by human interleukin-8 in the guinea-pig 79, 312-318.

20.

2. Kopaniak, of acute

R.

differentiation two cytokines.

B.B.

in bone alveolar

R.M.,

diford,

Eur.

endotoxins.

to

Dale, MM. (1989) The neutrophil leucocyte. In Textbook of immunopharmacotogy (MM. Dale andJ.C. Foreman, eds), Blackwell Scientific, London, 37-55.

depends

Bacterial

Borojevic,

and by

Vargaftig,

production guinea pig

REFERENCES H. (1992)

eosinophils

3042-3050.

93-97. 14.

its

Brade,

human

H.S.,

Lipopolysaccharide-induced

E.T., 26-33.

27,

PP., Fontaine, B., David, from the U937 cell line

factor

138,

proliferation are controlled

chemota.xis

1. Rietschel, 267 (2),

accumulation

Immunopharinacotogy,

Elsas,

ofa

the

larvae.

granulocyte granulomas

17.

The authors thank Dr. P.F. Weller (Beth Israel Hospital, Boston, MA) for the interest and critical correction of the manuscript. This study was supported by grants from CNPq (Brazil).

eosinophil

LPS.

131-136.

the

ACKNOWLEDGMENTS

pleural

by

Meheus,

L.A.,

Van Beeumen, Identification

Bozza

controls

in rabbit Fransen,

J.J., by

el at.

LPS-induced

tumor

macrophages.j L.M.,

Clin.

necrosis

85,

Raymackers,J.G.,

Van Bun, SM., microsequencing

LPS-induced

Invest.

factor

1108-1118.

Blockx,

HA.,

Van de Voorde, A. (1993) of lipopolysaccharide-

pleural

eosinophilia

157

induced proteins secreted by mouse macrophages. j Immunot. 151, 1535-1547. 32. Maimone, D., Reder, AT., Gregory, S. (1993) T cell lymphokine-induced secretion of cytokines by monocytes from patients with multiple sclerosis. Cell. Immunot. 146, 96-106. 33. Strieter, R.M., Remick, D.G., Lynch, J.P., III, Spengler, RN., Kunkel, S.L. (1989) Interleukin-2-induced tumor necrosis factor-alpha (TNF-a) gene expression in human alveolar macrophages and blood monocytes. Am. Rev. Respir. Dis. 139, 335-342. 34. Numerof, R.P., Aronson, FR., Mier, J.W. (1988) IL-2 stimulates the production of IL-la and IL-1f3 by human peripheral

158

Journal

of Leukocyte

Biology

Volume

56,

August

1994

blood 35.

mononuclear

Arenzana-Seisdedos,

cells. F.,

j Immunot. 141, 4250-4257. Virelizier, J.L., Fiers, W. (1985)

ferons as macrophage-activating factors. III. Preferential of interfemn-y on the interleukin 1 secretory potential or aged human monocytes. j Immunot. 134, 2444-2448. 36.

37.

Nedwin,

G.E.,

Svedersky,

L.P.,

Bringman,

T.S.,

Inter-

effects of fresh

Palladino,

MA., Goeddel, DV. (1985) Effect ofinterleukin 2, interferon--y, and mitogens on the production of tumor necrosis factors a and s.f Immunot. 135, 2492-2497. Hart, PH., Whitty, GA., Picolli, D.S., Hamilton, J.A. (1989) Control by IFN-’y and PGE2 ofTNF-a and IL-i production by human monocytes. Immunology 66, 376-383.