A Study to Find Out How Safe and Effective Gammaplex® is in Young People With Primary Immunodeficiency

Inclusion Criteria:

- The subject is between the ages of or is equal to 2 and 16 years of age, of either
sex, belonging to any ethnic group, and above a minimum weight of 10 kg. This weight
is based on the amount of blood required for testing.

- The subject has a primary immunodeficiency disease, which has as a significant
component of hypogammaglobulinemia and/or antibody deficiency (e.g. common variable
immunodeficiency, X-linked and autosomal forms of agammaglobulinemia, hyper-IgM
syndrome, Wiskott-Aldrich Syndrome). NB Isolated deficiency of a single IgG
subclass, or of specific antibodies without hypogammaglobulinemia per se, does not
qualify for inclusion.

- Subjects already receiving IGIV replacement therapy require the following before
their first infusion of Gammaplex:

- Documented IGIV dose(s) and treatment intervals for the last 2 consecutive routine
IGIV treatments (one of which can be the screening visit result). The previous doses
should also meet the following conditions before study entry: Have not changed by ±
50% of the mean dose for at least 3 months; be between 300 and 800 mg/kg/infusion; be
given every 21-28 days, inclusive; be a licensed or investigational product (Phase
III or IIIb).

- Documented previous IgG trough levels for the last 2 consecutive routine IGIV
treatmentsfor the last 2 consecutive routine IGIV treatments: Maintained at least 300
mg/dL above baseline serum IgG levels (defined as before initiation of any gamma
globulin treatment for that subject); must be more than/equal to 600 mg/dL.

- If a subject is a female of child-bearing potential, she must have a negative result
on an HCG-based pregnancy test.

- If a subject is a female who is or becomes sexually active, she must practice
contraception by using a method of proven reliability for the duration of the study.

- The subject is willing to comply with all aspects of the protocol, including blood
sampling, for the duration of the study.

- The subject, if old enough (generally 6 years to 16), has signed a Child Assent Form
and the subject's parent or legal guardian has signed the Informed Consent Form, both
approved by the IEC/IRB.

Exclusion Criteria:

- Has not been treated with IGIV (treatment naive subject)

- The subject has a history of any severe anaphylactic reaction to blood or any
blood-derived product.

- The subject is known to be intolerant to any component of Gammaplex, such as sorbitol
(i.e. intolerance to fructose).

- The subject has selective IgA deficiency, history of reaction to products containing
IgA, or has a history of antibodies to IgA.

- Subjects who have completed the study and subjects who have withdrawn cannot
participate in the study for a second time.

- The subject is currently receiving, or has received, any investigational agent, other
than an immune serum globulin (ISG) preparation that is being evaluated in a Phase
III or IIIb study, within the prior 3 months.

- The subject has been exposed to blood or any blood product or derivative within the
last 6 months, other than a commercially available IGIV or other forms of
commercially available and licensed ISG. If an unlicensed ISG product that is in
Phase III or IIIb has been given, the subject cannot be infused with Gammaplex until
20 days after the last dose was given.

- The subject is pregnant or is nursing.

- The subject, at screening, has levels greater than 2.5 times the upper limit of
normal as defined at the central laboratory of any of the following: (Alanine
transaminase (ALT); Aspartate transaminase (AST) Lactate dehydrogenase (LDH)).

- The subject has a severe renal impairment (defined as serum creatinine greater than 2
times the upper limit of normal or BUN greater than 2.5 times the upper limit of
normal for the range of the laboratory doing the analysis); the subject is on
dialysis; the subject has a history of acute renal failure.

- The subject is known to abuse alcohol, opiates, psychotropic agents, or other
chemicals or drugs, or has done so within the past 12 months.

- The subject has a history of DVT, or thrombotic complications of IGIV therapy.

- The subject suffers from any acute or chronic medical condition (e.g. renal disease
or predisposing conditions for renal disease, or protein losing state) that, in the
opinion of the investigator, may interfere with the conduct of the study.

- The subject has an acquired medical condition, such as, chronic or recurrent
neutropenia (ANC < 1000 x 109/L) or AIDS known to cause secondary immune deficiency,
or is post or recovering from hematopoietic stem cell transplantation.

- The subject is receiving the following medication: Systemic long-term
corticosteroids (i.e. not intermittent or burst, daily, >1 mg of prednisone
equivalent/kg/day).

- The subject is receiving Immunosuppressive or Immunomodulatory drugs.

- The subject has non-controlled arterial hypertension.

- The subject has anemia (hemoglobin <10 g/dL) at screening.