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Major histocompatibility complex class II antigen expression is suppressed by estradiol in cardiac allografts
ELSEVIEK
Major Histocompatibility Complex Class II Antigen Expression Is Suppressed by Estradiol in Cardiac Allografts H. Lou, T. Kodama,
Y.N. Wang, N.M. Katz, P.W. Ramwell,
C
HRONIC estradiol treatment inhibits transplant arteriosclerosis,‘~” probably through immune mechanisms. In general, estrogen increases the humoral immune response and attenuates the cell-mediated immune response. Thus, it is difficult to predict the effect of chronic cstradiol treatment on the allograft immune response and ultimately on transplant arteriosclerosis because allograft rejection involves both cell-mediated and humoral-mediated immune mechanisms. In the present study, the rabbit cardiac transplant model was used to evaluate the effect of chronic estradiol treatment on the immune activity and transplant arteriosclerosis in the cardiac allograft.
METHODS
Malt New Zealand White rabbits rcccivcd cardiac allografts from male Dutch Belted rabbits using end-to-side anastomosis of the aorta to the carotid artery and the pulmonary artery to the external jugular vein. The recipient animals were fed a 0.5% cholesterol diet and received cyclosporine A (10 mgikg per day IM) as well as either 17p cstradiol (E2) 100 &kg per day IM (N = 8) or placebo (N = 9) until killing. At 6 weeks posttransplantation the cardiac allografts were harvested and pressure-perfusion fixated. Five crosssections of each graft were embedded in paraffin. Sections (3 pm thick) were cut from each block for morphometry (elastin stain), and semiquantitation of rejection (hematoxylin-eosin stain) and immunohistochcmistry of major histocompatihility complex (MHC) class II antigen expression, T lymphocytes (T cells), and macrophagcs (MO) in graft coronary arteries. Monoclonal antibodies for MHC class II and T cells were gifts from Dr Libby (Brigham & Women’s Hospital, Boston) and those for MO were from Dr Gown (University of Washington, Seattle). Quantitation was done by evaluating the frequency of staining. An unpaired Student’s I test was used for comparisons between groups (I’ < .OS was considered significant).
Table 1. Immune Activity MHC
II+
29.5
Estradiol
0
P value
c.002
i
1.0
RESULTS
Hyperplasia Ma+ (%)
12.2
>.05
i-
DISCUSSION
From the Departments of Surgery (H.L., T.K., Y.N.W., N.M.K., M.L.H.) and Physiology and Biophysics (P.W.R.), Georgetown University Medical Center, Washington, DC, USA. Address reprint requests to Dr Marie L. Foegh, Georgetown University Medical Center, 4000 Reservoir Road NW, Building D, Room 398, Washington, DC 20007, USA.
(%)
11.3?
AND
MHC class II antigen expression was undetectable in any of the allograft coronary arteries from all of the E2-treated recipients, whereas it was abundantly expressed in the allograft coronary arteries from all placebo-trcatcd recipients. The frequency of staining of M0 was also significantly decreased. whereas the T-cell staining pattern remained unchanged. M0 and T-cell staining of the allograft coronary artery myointima was significantly less intensive in the E2-treated group (data not shown). Rejection was moderately but significantly less in the E2-treated group. These findings are associated with a 60% decrease in allograft coronary artery myointimal thickening in the E2-treated group compared with the placebo-treated group (Table 1). The E2-treatment-induced suppression of MHC class II antigen expression in the allograft coronary arteries may be related to the mechanism for prevention of transplant arteriosclerosis. This lack of MHC class II expression occurred with only a moderate change in vascular infiltration of T cells and M0, the latter being a professional MHC class 11 antigen-presenting cell. The decrease in MO infiltration in the vascular wall of the allograft from the E2-treated recipients coincides with our previous finding
T Cell’
(%) Placebo
and Myointimal
and M.L. Foegh
1.0
49.7
!I 7.0
1.8
16.1
? 4.0
of Cardiac Allografts* Rejection* score
c.02
Myointimal”
(O-4)
Thickenmg
2.7
? 0.1
44.3
2.1
*
17.9?
0.3
wer
(%) 3.6 1.5
“.002
c.05
*Data expressed as mean f SEM. +lmmune staining for MHC class II antigen, T cells, and Mm expressed as frequency of positive stained vessels ‘Re]ectlon scored according to the guldelines of the International Society for Heart and Lung Transplantation. “Myointimal thickening IS expressed as intimal area wer total vessel area x 100%
t
total
vessels
examined
0041-l 345/97/$17.00 PII so041 -1345(97)00534-4
0 1997 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
2626
Transplantation
Proceedings,
29, 2626-2627
(1997)
SUPPRESSION
2627
OF MHC CLASS II ANTIGEN
that chronic estradiol (100 &kg per day) treatment of the recipients is associated with an absence of M0 in the myointima and inhibition of myointimal proliferation.‘,’ Estrogens are known to increase the humoral immune response and thus might be expected to enhance graft arteriosclerosis and rejection. This did not occur in our studies. To the contrary, we observed reduced immune activities in the cardiac allografts, including that in the myointima of the coronary arteries. The animals are immunosuppressed with cyclosporine A and, based on this, E2 further enhances immunosuppression. Thus, E2 treatment
has a beneficial through immune
effect on graft mechanisms.
arteriosclerosis,
probably
REFERENCES
1. Foegh ML, Khirabadi BS, Nakanishi T, et al: Transplant Proc 19:90, 1987 2. Cheng LP, Kuwahara M, Jacobsson J, et al: Transplantation 52~967, 1991 3. Foegh ML, Asotra S, Howell MH, et al: J Vast Surg 19:722, 1993 4. Lou H, Kodoma T, Zhao YJ, et al: Circulation 94:3355, 1996
Major Histocompatibility Complex Class II Antigen Expression Is Suppressed by Estradiol in Cardiac Allografts H. Lou, T. Kodama,
Y.N. Wang, N.M. Katz, P.W. Ramwell,
C
HRONIC estradiol treatment inhibits transplant arteriosclerosis,‘~” probably through immune mechanisms. In general, estrogen increases the humoral immune response and attenuates the cell-mediated immune response. Thus, it is difficult to predict the effect of chronic cstradiol treatment on the allograft immune response and ultimately on transplant arteriosclerosis because allograft rejection involves both cell-mediated and humoral-mediated immune mechanisms. In the present study, the rabbit cardiac transplant model was used to evaluate the effect of chronic estradiol treatment on the immune activity and transplant arteriosclerosis in the cardiac allograft.
METHODS
Malt New Zealand White rabbits rcccivcd cardiac allografts from male Dutch Belted rabbits using end-to-side anastomosis of the aorta to the carotid artery and the pulmonary artery to the external jugular vein. The recipient animals were fed a 0.5% cholesterol diet and received cyclosporine A (10 mgikg per day IM) as well as either 17p cstradiol (E2) 100 &kg per day IM (N = 8) or placebo (N = 9) until killing. At 6 weeks posttransplantation the cardiac allografts were harvested and pressure-perfusion fixated. Five crosssections of each graft were embedded in paraffin. Sections (3 pm thick) were cut from each block for morphometry (elastin stain), and semiquantitation of rejection (hematoxylin-eosin stain) and immunohistochcmistry of major histocompatihility complex (MHC) class II antigen expression, T lymphocytes (T cells), and macrophagcs (MO) in graft coronary arteries. Monoclonal antibodies for MHC class II and T cells were gifts from Dr Libby (Brigham & Women’s Hospital, Boston) and those for MO were from Dr Gown (University of Washington, Seattle). Quantitation was done by evaluating the frequency of staining. An unpaired Student’s I test was used for comparisons between groups (I’ < .OS was considered significant).
Table 1. Immune Activity MHC
II+
29.5
Estradiol
0
P value
c.002
i
1.0
RESULTS
Hyperplasia Ma+ (%)
12.2
>.05
i-
DISCUSSION
From the Departments of Surgery (H.L., T.K., Y.N.W., N.M.K., M.L.H.) and Physiology and Biophysics (P.W.R.), Georgetown University Medical Center, Washington, DC, USA. Address reprint requests to Dr Marie L. Foegh, Georgetown University Medical Center, 4000 Reservoir Road NW, Building D, Room 398, Washington, DC 20007, USA.
(%)
11.3?
AND
MHC class II antigen expression was undetectable in any of the allograft coronary arteries from all of the E2-treated recipients, whereas it was abundantly expressed in the allograft coronary arteries from all placebo-trcatcd recipients. The frequency of staining of M0 was also significantly decreased. whereas the T-cell staining pattern remained unchanged. M0 and T-cell staining of the allograft coronary artery myointima was significantly less intensive in the E2-treated group (data not shown). Rejection was moderately but significantly less in the E2-treated group. These findings are associated with a 60% decrease in allograft coronary artery myointimal thickening in the E2-treated group compared with the placebo-treated group (Table 1). The E2-treatment-induced suppression of MHC class II antigen expression in the allograft coronary arteries may be related to the mechanism for prevention of transplant arteriosclerosis. This lack of MHC class II expression occurred with only a moderate change in vascular infiltration of T cells and M0, the latter being a professional MHC class 11 antigen-presenting cell. The decrease in MO infiltration in the vascular wall of the allograft from the E2-treated recipients coincides with our previous finding
T Cell’
(%) Placebo
and Myointimal
and M.L. Foegh
1.0
49.7
!I 7.0
1.8
16.1
? 4.0
of Cardiac Allografts* Rejection* score
c.02
Myointimal”
(O-4)
Thickenmg
2.7
? 0.1
44.3
2.1
*
17.9?
0.3
wer
(%) 3.6 1.5
“.002
c.05
*Data expressed as mean f SEM. +lmmune staining for MHC class II antigen, T cells, and Mm expressed as frequency of positive stained vessels ‘Re]ectlon scored according to the guldelines of the International Society for Heart and Lung Transplantation. “Myointimal thickening IS expressed as intimal area wer total vessel area x 100%
t
total
vessels
examined
0041-l 345/97/$17.00 PII so041 -1345(97)00534-4
0 1997 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
2626
Transplantation
Proceedings,
29, 2626-2627
(1997)
SUPPRESSION
2627
OF MHC CLASS II ANTIGEN
that chronic estradiol (100 &kg per day) treatment of the recipients is associated with an absence of M0 in the myointima and inhibition of myointimal proliferation.‘,’ Estrogens are known to increase the humoral immune response and thus might be expected to enhance graft arteriosclerosis and rejection. This did not occur in our studies. To the contrary, we observed reduced immune activities in the cardiac allografts, including that in the myointima of the coronary arteries. The animals are immunosuppressed with cyclosporine A and, based on this, E2 further enhances immunosuppression. Thus, E2 treatment
has a beneficial through immune
effect on graft mechanisms.
arteriosclerosis,
probably
REFERENCES
1. Foegh ML, Khirabadi BS, Nakanishi T, et al: Transplant Proc 19:90, 1987 2. Cheng LP, Kuwahara M, Jacobsson J, et al: Transplantation 52~967, 1991 3. Foegh ML, Asotra S, Howell MH, et al: J Vast Surg 19:722, 1993 4. Lou H, Kodoma T, Zhao YJ, et al: Circulation 94:3355, 1996