The immune response consists of two main components: humoral immunity represented by B lymphocytes and cellular immunity maintained by the T lymphocytes. Immunoglobulins, produced by B– lymphocytes, are the main mediators of humoral immunity, and deficiencies at this level affect the body’s response to infection. Plasmocytes produce nine antibody izotypes: immunoglobulins G (IgG 1, lgG2, lgG3, lgG4), immunoglobulins M (IgM), immunoglobulins A (lgA1, lgA2), immunoglobulins D (IGD) and immunoglobulins E (IgE). Primary hypogammaglobulinemias are characterized by the occurrence of recurrent infections and, paradoxically, by the occurrence of autoimmune diseases. Characteristic for these diseases is that symptoms occur at 7–9 months after birth, when transplacental antibody titers transmitted from the mother decrease, and the infant’s body is unable to synthesize them to normal levels. Primary hypogammaglobulinemias are transmitted genetically, but mutations at the molecular level are still not fully understood. The most common are: Bruton agammaglobulinemia , transient newborn hypogammaglobulinemia, selective immunoglobulin deficiency and variable common immunodeficiency. Treatment consists of monthly antibiotics and immunoglobulins, depending on antibody titers (except for IgA deficiency).