Which of the following Fibrinolytic is antigenic?
The clinically important fibrinolytic are:
1. Streptokinase
2. Urokinase
3. Alteplase (rt-PA)
4. Reteplase
5. Tenecteplase
Streptokinase:

It is obtained from Beta hemolytic Streptococci group C.
It is inactive as such: combines with circulating plasminogen to form an activator complex which then causes limited proteolysis of other plasminogen molecules to plasmin.
Antistreptococcal antibodies present due to past infections inactivate a considerable fraction of the initial dose of Stk: a loading dose is necessary for the beginning. Its t1/2 is estimated to be 30-80 min.
Streptokinase is antigenic; can cause hypersensitivity reactions and anaphylaxis, especially when used second time in a patient.
Repeat doses are also less effective due to neutralization by antibodies. Fever is common, hypotension and arrhythmias are reported.
Urokinase
Alteplase
Tenecteplase
Streptokinase