diff --git a/rest_framework/exceptions.py b/rest_framework/exceptions.py
index 425a72149..2bd21de3b 100644
--- a/rest_framework/exceptions.py
+++ b/rest_framework/exceptions.py
@@ -13,47 +13,40 @@ class APIException(Exception):
     Base class for REST framework exceptions.
     Subclasses should provide `.status_code` and `.detail` properties.
     """
-    pass
+    status_code = status.HTTP_500_INTERNAL_SERVER_ERROR
+    default_detail = ""
+
+    def __init__(self, detail=None, status_code=None):
+        self.status_code = status_code or self.status_code
+        self.detail = detail or self.default_detail
 
 
 class ParseError(APIException):
     status_code = status.HTTP_400_BAD_REQUEST
     default_detail = 'Malformed request.'
 
-    def __init__(self, detail=None):
-        self.detail = detail or self.default_detail
-
 
 class AuthenticationFailed(APIException):
     status_code = status.HTTP_401_UNAUTHORIZED
     default_detail = 'Incorrect authentication credentials.'
 
-    def __init__(self, detail=None):
-        self.detail = detail or self.default_detail
-
 
 class NotAuthenticated(APIException):
     status_code = status.HTTP_401_UNAUTHORIZED
     default_detail = 'Authentication credentials were not provided.'
 
-    def __init__(self, detail=None):
-        self.detail = detail or self.default_detail
-
 
 class PermissionDenied(APIException):
     status_code = status.HTTP_403_FORBIDDEN
     default_detail = 'You do not have permission to perform this action.'
 
-    def __init__(self, detail=None):
-        self.detail = detail or self.default_detail
-
 
 class MethodNotAllowed(APIException):
     status_code = status.HTTP_405_METHOD_NOT_ALLOWED
     default_detail = "Method '%s' not allowed."
 
     def __init__(self, method, detail=None):
-        self.detail = (detail or self.default_detail) % method
+        super(MethodNotAllowed, self).__init__((detail or self.default_detail) % method)
 
 
 class NotAcceptable(APIException):
@@ -61,7 +54,7 @@ class NotAcceptable(APIException):
     default_detail = "Could not satisfy the request's Accept header"
 
     def __init__(self, detail=None, available_renderers=None):
-        self.detail = detail or self.default_detail
+        super(NotAcceptable, self).__init__(detail)
         self.available_renderers = available_renderers
 
 
@@ -70,19 +63,19 @@ class UnsupportedMediaType(APIException):
     default_detail = "Unsupported media type '%s' in request."
 
     def __init__(self, media_type, detail=None):
-        self.detail = (detail or self.default_detail) % media_type
+        super(UnsupportedMediaType, self).__init__((detail or self.default_detail) % media_type)
 
 
 class Throttled(APIException):
     status_code = status.HTTP_429_TOO_MANY_REQUESTS
-    default_detail = "Request was throttled."
+    default_detail = 'Request was throttled.'
     extra_detail = "Expected available in %d second%s."
 
     def __init__(self, wait=None, detail=None):
+        super(Throttled, self).__init__(detail)
+
         import math
         self.wait = wait and math.ceil(wait) or None
         if wait is not None:
-            format = detail or self.default_detail + self.extra_detail
-            self.detail = format % (self.wait, self.wait != 1 and 's' or '')
-        else:
-            self.detail = detail or self.default_detail
+            format = self.detail + self.extra_detail
+            self.detail = format % (self.wait, self.wait != 1 and 's' or '')
\ No newline at end of file