Which statement best differentiates SCID from X-linked agammaglobulinemia?

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Multiple Choice

Which statement best differentiates SCID from X-linked agammaglobulinemia?

Explanation:
The main concept is how different parts of the immune system are affected. SCID shows failure of both cellular and humoral immunity, meaning T cells and B cells are impaired, so you see low CD4 (and often CD8) counts along with low immunoglobulins. X-linked agammaglobulinemia, on the other hand, is a block in B-cell development so immunoglobulins are low, but T cells, including CD4 T cells, are typically normal. So the best statement is that SCID has decreased CD4 counts and decreased immunoglobulins, reflecting both T-cell and B-cell problems, while XLA has decreased immunoglobulins only with normal CD4 counts because T cells are not directly affected.

The main concept is how different parts of the immune system are affected. SCID shows failure of both cellular and humoral immunity, meaning T cells and B cells are impaired, so you see low CD4 (and often CD8) counts along with low immunoglobulins. X-linked agammaglobulinemia, on the other hand, is a block in B-cell development so immunoglobulins are low, but T cells, including CD4 T cells, are typically normal.

So the best statement is that SCID has decreased CD4 counts and decreased immunoglobulins, reflecting both T-cell and B-cell problems, while XLA has decreased immunoglobulins only with normal CD4 counts because T cells are not directly affected.

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